The National Institute of Standards and Technology (NIST) fulfills a vital role in national security: employing the sort of people who would, if they got bored, take over the world. It takes a specific kind of person to run the persnickety gravitational calculations of exactly how fast clocks tick on Mars relative to the Earth.

Thanks to NIST, two of these people have recently published their calculations, instead of building a lair under a volcano to perform evil experiments. They found that Mars time runs faster than Earth time, and considerably messier.

The purpose of clock rate models

In strong gravitational fields, time flows more slowly. Albert Einstein first described this effect, known as time dilation, in his 1915 theory of general relativity. Scientists working in precision timekeeping must account not only for the Earth's gravity, but also that of the Sun and Moon.

They have become very good at that. The evidence is on your phone: the accuracy of GPS is thanks to minute adjustments to clock rates in different locations around the Earth.

Future spacefarers will need to know the exact time on Mars relative to the Earth. Any kind of precision location system, such as GPS, depends on clock rate conversions. The new paper from NIST models the gravitational field on Mars at different points throughout its orbit to predict what that clock rate should be. They double-check their results using in-situ gravitational observations from Mars.

Mars' messy time

Modelling Martian time is a lot more complicated than it is for the Earth. Not only is it harder to actually take measurements that would allow scientists to check their math, but the math itself also involves more factors.

Mars' lower mass means gravity is a lot weaker on its surface than on Earth. Even without external effects, Martian time flows faster than Earth time.

But the Mars time to Earth time conversion depends on a lot more than Mars's gravitational field. The biggest complication for time on Mars is the eccentricity of its orbit. Eccentricity describes how elongated and oval-shaped an orbit is, as opposed to circular. Since Mars' orbit is considerably more eccentric than Earth's, its distance from the Sun varies much more.

Mars's lower mass, only 10% of the Earth's, also makes it easier for other bodies in the Solar System to push it around. While the motion of Mars doesn't affect the Earth's gravity much, the motion of Earth matters a lot to Mars.

The ever-changing locations of the Sun and the Earth push and pull on the surface gravity of Mars and, consequently, its clock rate.

We understand Earth time 100 times better than Mars time

Although Mars time changes over the course of a Martian year, the authors found an average difference of 421.5 microseconds (millionths of a second, or μs) per day between Mars and the Earth. It doesn't sound like much, but think of it this way: For every day that passes on Earth, Mars falls behind our clocks by 421.5 μs. If we don't model and compensate for the difference, that's enough to render 5G wireless, for instance, totally useless.

By predicting this discrepancy, the authors have theoretically enabled 5G cell service on Mars, although some minor technological advancements will be necessary to make this happen. But their model does come with big error bars.

Make no mistake: the new model of Martian time is vastly more precise than the previous model. (The previous model was created by the exact same people who made the new one, because NIST only employs people with worrying dedication.) Nonetheless, it fits the data about a hundred times worse than the current best model of Moon to Earth time conversion. You'll never guess who the authors are on that one.

When they compare their model of clock rate to real gravitational observations from Mars, their guesses are only off by an average of 100 ns (a billionth of a second) every day. This is astoundingly precise, but still a hundred times worse than their errors on the Moon, which are about 1 ns every day. Mars is a messier place to visit than the Moon, and time runs strangely there.

Our view of space is under threat from the rapidly growing cloud of satellites circling the planet. Streaks of reflected light from satellites are ruining space telescope images all over the world.

The problem stems from the explosion of satellite megaconstellations being launched into orbit.

“Until now, most light pollution came from cities and vehicles,” says Alejandro Borlaff of NASA. "[Now] telecommunication satellite constellations is rapidly affecting astronomical observatories worldwide."

It's bound to get worse. Companies such as SpaceX, OneWeb, Amazon, and others have plans to launch hundreds of thousands of small satellites into low orbit over the next decade. Currently, more than 15,000 satellites orbit the Earth, up from 2,000 just a few years ago. But that number could balloon to more than half a million by the late 2030s.

These satellites are already a problem. Long-exposure images at twilight or dawn is the ideal way to capture faint cosmic objects. But bright satellite trails now routinely mar the field of view, affecting astronomers' ability to collect data. 

Space telescopes also affected

The problem isn’t limited to telescopes on Earth. Even telescopes in space, including the Hubble Space Telescope, are not immune to this form of light pollution. Up to 33 percent of Hubble’s images could be contaminated with streaks by the mid-2030s if these satellite megaconstellations expand as planned. Others could see more than 95 percent of their exposures affected.

As a satellite crosses a telescope’s field of view, the reflected sunlight creates a bright line or “photobomb” across the image.

“As telescopes stare at the Universe attempting to unveil distant galaxies, planets, and asteroids, satellites sometimes cross in front of the cameras, leaving bright traces of light that erase the dim signal that we receive from the cosmos,” said Borlaff. 

Last year, the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky issued a series of recommendations for satellite companies to help protect our view of space. Their proposals include making the satellites less reflective and adjusting orbits to minimize the times when they cross busy observation zones. 

Despite its unmemorable name, J2322-2650 is a strange system. A Jupiter-sized exoplanet orbits an energetic neutron star, which constantly bombards it with gamma rays. Now, a team of astronomers has published its observations of the planet. They discovered strong westerly winds and an atmosphere unlike anything else.

So is it really a planet at all?

Pulsars and their companions

When massive stars die, they jettison their outer layers in a supernova. No longer able to support itself through nuclear fusion, the core collapses in on itself. If it's big enough, it forms a black hole. If it's not, it leaves behind a neutron star.

In many ways, these zombie stars are more dramatic objects than black holes. Many emit violent bursts of gamma rays and X-rays, the sort of light that would tear apart human cells. Periodic radio emission is also common, flung out from near the surface of the neutron star as a result of off-kilter magnetic fields. (Exactly how close to the surface this emission begins, and through what mechanism, remains a mystery.)

Neutron stars that emit in the radio band are known as pulsars, or zombie stars, because they are remnants of massive dead stars. These radio pulses are so regular, so seemingly artificial, that their discoverer, Jocelyn Bell, jokingly referred to them as "little green men."

Astronomers observe the radio waves of pulsars to study all sorts of phenomena. They can detect companion stars orbiting the pulsar -- everything from rocky planets to other neutron stars -- using slight delays in the pulse arrival times at the telescope.

That's how the team behind a new study on J2322-2650 knew to point the James Webb Space Telescope at this source, when no traditional exoplanet survey would have noticed the faint Jupiter-like companion. (In all but a few exciting cases, pulsars do not emit visible light.)

Carbon winds on a lemon-shaped planet

Jupiter-like planets tend to have atmospheres composed mostly of hydrogen and helium, similar to the Sun. Heavier atoms like nitrogen, carbon, and oxygen allow molecules such as ammonia and methane to form. While no two gas giant exoplanets are the same, astronomers have never found anything like the companion of J2322-2650 before.

Instead of a hydrogen-based atmosphere, they found mostly helium and an absurd amount of carbon. Not hydrocarbon chains, which commonly occur in outer space, but pure molecular carbon. In solid form, pure carbon forms minerals like graphite and diamonds. There is no earthly analog for gaseous clouds of carbon -- even the darkest soot also includes lots of oxygen and hydrogen.

Team co-author Peter Gao said that the observations stunned him. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’ It's extremely different from what we expected.”

The weird planet's nearness to a pulsar enables its gaseous, carbon-rich atmosphere. The two are so close together that the pulsar's gravity keeps the companion pinned with one side always facing it, a process known as tidal locking. (The Moon, for instance, is tidally locked to the Earth). Because the near side of the companion is slightly closer to the pulsar than the far side, the difference in gravitational attraction stretches it out like a football.

So that's the companion of this zombie star: an elongated, tidally locked object covered in carbon winds, whose nearside is pummeled by gamma rays all the time and whose far side never sees light.

What is it?

Black widow pulsars

Black widow is one of those wretched, jargon-y pulsar terms that baffle most other astronomers, let alone the general public. But unlike many offbeat pulsar terms (just what is a birdie, anyway, and what does it mean to zap one?), black widow is descriptive. A black widow pulsar is one that, like a female black widow spider, is "eating" the light, fluffy atmosphere of its companion. Many of these companions are brown dwarfs, failed stars more similar to Jupiter than to our Sun.

Most astronomers consider brown dwarfs to be planets. Like Jupiter, they have hydrogen atmospheres rich with common molecules like methane, and more exotic iron and silicate compounds. They are not dominated by helium and pure molecular carbon.

Even if we assume this system represents the end-stage of classical black widow formation, where the pulsar has already stripped most of the atmosphere off its companion, the carbon remains an anomaly. Carbon and oxygen form at the same stage of stellar evolution, so there should be a lot more oxygen floating around its atmosphere.

The authors of the study discuss more exotic scenarios, like a merger between one helium and one carbon-oxygen white dwarf. But these still can't explain the carbon concentration they observed. We may know what this companion looks like now, but what it used to be remains a mystery.

Above, an artist's conception of the system, as the lemon-shaped planet orbits the pulsar. Imagery: NASA/JWST/ESA/CSA/Ralf Crawford (STScI)

A week ago, a bright green fireball shot across the sky above the Great Lakes in Michigan. At around 5:30 am, witnesses across Michigan, Ohio, Wisconsin and Indiana saw the meteor leave a vivid green streak until Lake Huron, where it exploded.

More than 40 individuals logged eyewitness reports with NASA and captured images of the eerie meteor. At the time, many were unsure of what they were actually seeing, but scientists at NASA and the American Meteorological Society have confirmed that this was a fragment of a comet hurtling at roughly 160,000kph.

The fragment became visible around 100km above Hubbard Lake, a tiny Michigan village west of Lake Huron, before traveling 132km and disintegrating at an altitude of 74km over Lake Huron.

Such fireballs are often associated with meteor showers, but NASA said this was a one-off explosion, unrelated to the Leonid meteor shower at the time.

"This event appears to have been caused by a small comet fragment," said NASA. "It was too small and too fast to have dropped any meteorites into Lake Huron."

The fragment's eerie emerald hue likely came from its chemical makeup, in particular, a high concentration of nickel. As the fragment burned up, the combination of heat and high speed caused the nickel to emit green light as it ionized.

Researchers have just discovered a giant crater 900m in diameter in southern China. Named the Jinlin crater, a new study confirms that the huge bowl-shaped formation in Guangdong Province came from an asteroid impact. The impact crater is also less than 10,000 years old, shockingly recent.

To confirm that it is an impact crater, researchers from China's Center for High Pressure Science sampled rock fragments. A huge object hitting the Earth at high speed brings immense forces to bear. This creates a crater, but it also leaves damage at a microscopic level. The shock waves create what are called "planar deformation features" in materials like quartz and feldspar.

These structures form only under the immense pressure of 10 to 35 gigapascals, which can only come from celestial body impacts.

Researchers collected quartz from Jinlin and looked for these visible pairs of shock-damage structures. They found them.

Hiding in plain sight

But not only is Jinlin an impact crater, but it's also a very young one. The rainy conditions in Guangdong and the loose soil that make up the rim mean the crater should erode fairly quickly. The fact that it hasn't means it must be fairly young.

To get a more exact idea, researchers looked at very small pieces of granite. The chemical weathering rate of granite under known local conditions is a fixed rate. Based on that, any fragment of granite under 30 centimeters created by the impact will take around 10,000 years to completely turn into soil. The fact that there are still some of these tiny granite fragments around means the impact occurred less than 10,000 years ago.

Ancient asteroid

Today, we have very little reason to fear sudden destruction by an asteroid. But significant impact events were something to fear in our recent past. In a press statement, lead author Ming Chen said that Jinlin crater "shows that the scale of impacts of small extraterrestrial objects on the Earth in the Holocene is far greater than previously recorded."

Based on the size of the crater, Chen's team estimates that the meteor itself was about 30 meters across. This makes it much, much smaller than the asteroid which killed off the dinosaurs, but thirty times the size of the object which burnt up over the Philippines last year. We don't know exactly what it was made of yet.

It's three times the size of Russia's Macha crater, which previously held the distinction of being the largest Holocene impact site.

While they did not leave any evidence of writing, people were living in the Guangdong region 10,000 years ago. They must have experienced quite a sight.

Mosses are some of the hardiest plants on Earth. These pioneer species can thrive in some of the most extreme environments on Earth. New research shows that mosses are even tougher than we thought. They can survive in space. 

The vacuum of space makes it nearly impossible for most living organisms to survive, but one species of moss, Phycomitrium patens, survived outside the International Space Station for nine months. Tomomichi Fujita, who led the study, was intrigued by mosses' ability to grow everywhere from Death Valley to Antarctica.

“I began to wonder: Could this small yet remarkably robust plant also survive in space?” he said in a statement. 

He and his research team selected Phycomitrium patens, commonly known as spreading earthmoss, because it is well-studied and widespread on Earth.

UV radiation the hardest to deal with

They began by testing how the moss would perform in a simulated space environment. “We anticipated that the combined stresses of space, including vacuum, cosmic radiation, extreme temperature fluctuations, and microgravity, would cause far greater damage than any single stress alone,” said Fujita. 

They tested juvenile moss, brood cells (specialized stem cells that are produced in stressful conditions) and sporophytes (the reproductive structures that produce spores). The biggest stressor to all three structures was UV radiation, but the sporophytes coped with it much better than both the juvenile moss and the brood cells. The next step was to see how the sporophytes actually handled space. 

In 2022, the research team brought hundreds of sporophytes to the ISS. The astronauts then attached the sporophytes to the outside of the space station for 283 days, after which they were brought back to Earth.

"We expected almost zero survival, but the result was the opposite," said Fujita. "Most of the spores survived. We were astonished by the extraordinary durability of these tiny plant cells."

Nine months in a vacuum

Over 80% of the sporophytes survived nine months in space and the journeys to and from the ISS. Of those, 89% were still able to germinate once they landed back on Earth.

The protective capsule around each spore might be the key to its success. It acts as both a chemical and physical barrier and absorbs the UV radiation that other structures in the plant could not cope with.

As well as this, almost all types of chlorophyll, the green pigment in photosynthesis, remained at normal levels. Only chlorophyll a declined by 20%. However, this did not seem to affect spore health. 

Based on the plants' success, computer models suggest that the spores could have actually survived for 15 years in space.

“This study demonstrates the astonishing resilience of life that originated on Earth," said Fujita. 

It doesn't look real, at first glance. There must be a green screen right behind the shadowed silhouette of a falling man. It must be AI-generated. But it's real: a snapshot of a man in freefall, eclipsing the high-resolution surface of the Sun behind him.

How?

Trigonometry preparation

Andrew McCarthy and Gabriel Brown came up with the idea for the shot while skydiving together. They knew it would be near-impossible.

"We had to find the right location, time, aircraft, and distance for the clearest shot, while factoring in the aircraft’s power-off glideslope for the optimal sun angle and safe exit altitude," wrote Brown on Instagram.

He volunteered to skydive for the project, while McCarthy, an experienced solar astrophotographer, would snap the shot. 

Brown posted screenshots of the math involved. In addition to the skydiving complications, the pair needed to calculate how far away the telescope should be to silhouette a man against sunspots and granulation (the pattern on the Sun's outer atmosphere made by little heat cells bursting).

These sunspots are tens of thousands of kilometers wide and 150 million kilometers away. The shot needed both the skydiver silhouette and the sunspots to be clear and visible. That wouldn't work if the silhouette is way smaller or larger than the sunspots. They had to fit into the frame at comparable sizes. This was one of the factors that set how far away from Brown the camera had to be. They calculated that the proper distance would be 1.5 miles, or 2.4 kilometers.

Four pilots and a paramotor

For maximum precision, McCarthy and Brown hired a paramotor pilot to give Brown a lift. They went through three pilots before finding Jim Hamberlin. Hamberlin was able to steer his paramotor directly in front of an active region on the Sun's surface. When McCarthy gave the call, Brown jumped from the motor, and Hamberlin revved it up out of the way of the central shot.

Typically, skydivers spend 10 seconds or so in freefall from Brown's 3,500-foot exit altitude before triggering their parachute. That's enough time for Brown to have reached terminal velocity at about 200kph -- the speed at which gravity balances with air resistance and a skydiver doesn't accelerate any further. (His head-down position would have given him an even faster terminal velocity, up to 320kph.) McCarthy filmed his freefall on a Lunt 60mm H-alpha camera and snapped single exposures on an ASI 1600mm.

One shot captured Brown's silhouette and the position of the Sun, but not the details of the solar chromosphere (the Sun's hot outer atmosphere) or its wider surface. As described in his highly readable write-up of his usual solar photography methods, McCarthy stacked hundreds of exposures. By tracking the Sun's minute motion through the sky, he prevented blurring while preserving the features of the chromosphere at that moment in time. The solar surface is highly turbulent, so the same sunspots a day later might have moved or faded.

Each exposure only covered a small tile of the solar surface, so for the fully zoomed-out version of the shot, McCarthy pieced them together into a composite image like a mosaic. (In fact, this method of imaging space objects is called mosaicing and is used in both astrophotography and scientific astronomy.)

Filters and focus

No matter how fast the shutter speed, a normal photo of the Sun oversaturates a camera's detector. That's why McCarthy used an H-alpha filter for this photo, like he uses for all his solar photography. "H-alpha" refers to a narrow frequency of reddish light that hydrogen emits when it decreases in energy.

With an H-alpha filter in place, photographs of the Sun only take in the outer edge of the chromosphere, where hydrogen is cooling and thus decreasing in energy. It's a favorite filter of astrophotographers because dramatic features such as sunspots and solar flares form on the chromosphere.

Unlike the chromosphere, humans are largely invisible in H-alpha. They reflect only what stray photons bounce off them from the Sun. That's why Brown's falling form stands out like a hole in space.

While keeping two objects of different distances in focus is usually difficult, especially with a long lens, McCarthy took the photo so far away from Brown that both he and the Sun came out sharp. They both fell within the so-called zone of focus that photographers are familiar with.

If you're interested in a print of either the close-up or full versions, you can find them on McCarthy's store, along with his other work. As for Brown, McCarthy reassured Redditors that he landed safely. And no, he wasn't anywhere near the Sun.

The Moon has a little-known companion -- a slightly lopsided dust cloud that never leaves its side. The cloud leans toward whichever side of the Moon happens to be facing the sun. After years of wondering, scientists think they have finally figured out what the cloud is and how it got its wonky shape. 

Micrometeoroids constantly strike the surface of the Moon. These are tiny bits of rock around 1mm in diameter that hurtle through space at high speeds. Several tons of this cosmic dust hit the Moon every day. The constant bombardment turns the small surface rocks into dust, forcing this lunar powder into the air. As it rises, it forms a huge cloud above the Moon. 

Though the cloud stretches for hundreds of kilometers, you can’t see it with the human eye.

“The maximum density measured was only 0.004 particles per cubic meter," Sebastian Verkecke, lead author of the new study, told Live Science. The density is not evenly spread throughout the cloud. It is always denser on the Moon’s daytime side, especially at the dawn terminator -- the line between light and darkness on the lunar surface. 

Researchers think the cloud is so lopsided due to the huge temperature fluctuations on the Moon. During the day, it can reach 285˚C, while nights can drop to -183˚C.

To test their hypothesis, they ran computer simulations of micrometeoroids hitting the lunar surface at different temperatures to mimic night and day on the Moon. The models showed how both dust and regolith responded. 

The results showed that heat makes a big difference. When the surface is warmer, the impacts blast more dust into space and send it higher. The compactness of the lunar soil also matters. Tightly packed surfaces released more dust when struck, while fluffier, looser surfaces tended to absorb more of the impact’s energy and throw up less material. All of this explains why the Moon’s dust cloud is thicker on the sunlit side, giving it a strangely lopsided shape.

When the micrometeoroids slam into the hot daytime surface, the heat makes the dust particles fly higher and spread farther. But when it hits the cold night surface, the dust doesn’t travel as far, and much less of it escapes. Over time, that creates a thicker dust cloud over the Moon’s sunlit side and a thinner one over the dark side.

The research team now wants to extend their study to look at other objects in our solar system. Mercury is of particular interest. Sitting closer to the sun, its daytime temperatures are significantly higher, which could create an even wonkier dust cloud. 

Astronomers have announced a candidate for the universe's first generation of stars. While sifting through observations of the earliest known galaxies, they flagged one small dwarf galaxy, GLIMPSE-16043. Unlike every galaxy we have observed before, it doesn't bear any signs of recycled stellar material.

Astronomers have theorized the existence of this first generation of stars, which formed not from the ashes of their ancestors but from primordial hydrogen and helium. Many candidates have previously cropped up, but none have won popular support. GLIMPSE-16043, however, may have what it takes to stand the test of time.

'Population III' Stars

The Big Bang only created four elements: hydrogen, helium, and tiny amounts of lithium and beryllium. No oxygen, no iron, no carbon. In short, none of the elements that make up our solid, dynamic world.

Those did not arrive until much later, when the first stars died in massive explosions called supernovae. Deep in the furnace of their cores, they had forged all of the elements up to iron. Their supernovae flung these elements out across interstellar space, seeding the gas with metals that would work their way into the next generation of stars. (Astronomers call any atom heavier than helium a metal, presumably because they want to drive chemists into a blind rage.)

When early astronomers observed the Milky Way, they found this second generation of stars lurking in the ancient center of the galaxy and at the far-flung edges. They called them Population II stars to distinguish them from the much more metallic, familiar Population I stars that make up the Milky Way. These include our Sun.

By the time astronomers got around to theorizing the existence of an even earlier generation of stars, the naming convention was set. The first stars in the universe are Population III.

A galaxy of only hydrogen and helium

People cannot exist without metals. Planets cannot exist without metals. Not even the dust grains that float in interstellar space can exist without metals. Without metals, there are only clouds of gas and stars.

That's what would comprise this possible candidate for Population III stars, a dwarf galaxy from only 900 million years after the Big Bang. GLIMPSE-16043 is only visible to us because it lies behind a much larger, much more nearby galaxy. The gravity of that foreground galaxy magnifies the light of GLIMPSE-16043 and reroutes it toward us. The James Webb Space Telescope (JWST) excels at photographing these "gravitationally lensed" galaxies.

The team that identified GLIMPSE-16043 investigated thousands of lensed galaxies observed with the JWST. GLIMPSE-16043 was the only one that matched their criteria. Hydrogen makes galaxies redder, so to identify galaxies dominated by hydrogen, the team restricted their search to galaxies that appear brighter when photographed through a red filter.

Then they used how bright a galaxy is under different colored filters to calculate its age. They kept only the hydrogen-dominated galaxies that dated from 700 million to 1.2 billion years after the Big Bang. That's when Population III stars would have existed.

GLIMPSE-16043 passed these tests with flying colors. At about 900 million years after the Big Bang, it seems to have almost no metals. When we look at this tiny little dot on a pixelated image, we may be looking at some of the first stars in the universe.

Confirming this will be difficult. The dwarf galaxy is very faint, and the JWST is probably not sensitive enough to do anything other than image it in different color filters. These filters are equivalent to putting giant buckets out in the rain to catch all the water you can. They miss the fine detail in each raindrop that would reveal the presence or lack of metals.

If this galaxy is indeed made of Population III stars, it is probably one of the last stragglers from that era. We may need to wait for a better bucket to confirm the nature of GLIMPSE-16043. Fortunately, the galaxy isn't going anywhere.

If you have a favorite planet or star, you're in good company. Astronomers who devote their lives to the study of peculiar outer space objects are all too happy to gush about the ones they like best. From the cradles of new planets to the violent graveyards of massive stars, here are some of the answers we got for the question: "What's your favorite thing in outer space?"

A planet factory far from Earth

Yifan Zhou is an assistant professor of Astronomy at the University of Virginia, where he studies exoplanets with high-powered optical and infrared telescopes like the James Webb Space Telescope. Predictably, his favorite thing in space is a distant star with planets orbiting it.

This system, PDS 70, was "One of the first objects I have looked at for my first research project in undergrad," Zhou says. "My analysis led to a sort of failed project. The object that we thought was a planet of PDS 70 turned out to be a background star."

But Zhou and his advisor's intuition that PDS 70 had planets turned out to be correct. In fact, the baby super-Jupiter orbiting PDS 70 was the first exoplanet to be directly imaged. In groundbreaking images from the European Southern Observatory, a glowing young planet carves out rings in the dust and gas accreting onto the star.

"The discovery reminded me of my undergraduate project," says Zhou. Inspired, he led a Hubble project that tracked how quickly gas is falling onto the young super-Jupiter. He credits that work with helping boost his career. "I'm still writing proposals about it now."

A star with a vaporized moon stuck in orbit

Most star systems are too far away and too faint to directly image any planets around them. Claire Rogers is a graduate student in Physics at the University of California Irvine who researches stars whose atmospheric fluctuations mimic the signs of planets. Her favorite object in space is Tabby's Star, an exoplanet system found in the Kepler survey, which she loves for its "super weirdly shaped transits." Transits are dips in starlight brought on by a planet passing in front of it.

The transits across Tabby's Star are so dramatic that they inspired theories of alien civilizations.

"For a bit, people thought it might be an artificial megastructure blocking the light, but it is probably actually dust from an exomoon that got broken up around it," she says.

Tabby's Star is a dramatic example of a common source of confusion for planet hunters: Dips in stellar brightness that hint at planets, but might just be the star.

"Stars vary naturally in their emission, and the variations...are roughly comparable to the variations we would expect from a small planet," Rogers explains.

A flashing star system hidden by dust

Dillon Dong, a postdoctoral fellow at the National Radio Astronomy Observatory in Socorro, New Mexico, picked a favorite star whose light varies even more wildly: Eta Carina.

Throughout the 19th century, the previously unobtrusive Eta Carina began to glow brighter and brighter. Once barely visible to the human eye, by 1837, it outshone Rigel. The following year, it dimmed once more. It kept fluctuating until 1845, when it rocketed up to the vaulted place of second-brightest star in the sky. Then it began to fade. By 1886, it was no longer visible at all.

This was not a supernova, those violent stellar death throes that go off in a blink and fade steadily over time. Eta Carina was inconsistent. Something stranger was going on.

"This system shows just how much we have to learn about the dramatic pre-explosion lives of massive stars," enthuses Dong, who researches radio signals from exotic stars. "The cause of the brightening was a great eruption where the star blew out dozens of solar masses of material, forming the Homunculus Nebula."

The dust obscures much of the inner workings of the Eta Carina system, including further evidence of what exactly happened to it in the 19th century. Many of the theories involve dramatic binary interactions. In one scenario, the system originally had three stars, and the brightening came from a collision between two of them. Another theory suggests that one star may have stolen matter from another as it passed by. It's hard to tell, because Eta Carina is unique in our sky. No other system exhibits fluctuations so shrouded in mystery.

"The thing that really gets me is that most massive stars are in binaries, triples, etc," says Dong. "This kind of thing surely happens all the time in the universe."

A dramatic stellar corpse

When massive stars like Eta Carina run out of fuel to burn, they explode into supernovae and leave behind neutron stars like the memorably named 1E2259+586, the favorite object of Victoria Kaspi. Kaspi is a professor physics at McGill University and director of the Trottier Space Institute. She observed 1E2259+586 uneventfully for years before it suddenly lit up with X-ray flares, thereby helping her answer a long-standing mystery.

Neutron stars are the condensed remnants of massive stars. Within them, frictionless superfluids flow through a crystal lattice of neutrons. They weigh more than our Sun, but all that matter is packed into a ball the size of San Francisco.

Some neutron stars emit regular X-rays through magnetic activity near their surfaces.  1E2259+586 is one of these, but its period is unusually low. This source, and a handful of other slow X-ray pulsars, were the focus of conflicting theories.

One theory posited that the slow X-ray emission was driven by material trickling onto the neutron star's surface. The other, more dramatic interpretation predicted that the rotation rate was slow because of a supersized magnetic field holding the neutron star back. This kind of theoretical object, called a magnetar, could also potentially explain neutron stars that emit sporadic low-energy gamma rays.

Kaspi monitored the slow X-ray pulsar 1E2259+586 for years with the Rossi X-ray Timing Explorer (RXTE), trying to determine its nature. "It was getting a little dull," she says of her now-favorite source. "Then one day, the [principal investigator] of RXTE called me on the phone to say it was having major X-ray bursts during one of my observations!"

These X-ray bursts were leagues more intense than the regular, repetitive emission Kaspi had observed up until then. Only the magnetar theory predicted this kind of behavior from anomalous X-ray pulsars like 1E2259+586. 

"In that instant, I knew those observations had proven it was a magnetar. It was a great feeling, a true 'eureka' moment."

The first light in the Universe

Up till now, all the astronomers in this article have been observers who use telescopes to advance our knowledge. I was curious to know what an astronomer who works in the field of computing would pick as the coolest thing in outer space, so I asked Mariangela Lisanti, a professor of Physics at Princeton. Her simulations predict how different models for dark matter affect galaxies.

"Am I allowed to say the Cosmic Microwave Background?" she says.

Her hesitation comes from the fact that the CMB is so much bigger and more singular than other sources in space. It's like being asked what your favorite rock is and saying the Moon. The CMB is the remnant radiation propagating through all space that has been traveling toward us since the entire universe was on fire. If you tune your TV between channels, then somewhere between 1%-10% of the static will be from the CMB. (Exactly how much depends on the frequency.)

But astronomers use the tiny variations across the CMB to probe everything from the formation of the first galaxies to how gravity behaves at the subatomic scale. It absolutely counts as a cool thing in space. It's kind of the ultimate cool thing in space.

The European Space Agency (ESA) has just made it possible for all wannabe astronauts to fly over the Red Planet -- virtually. In a mesmerizing new video, viewers can glide over the ancient Shalbatan Vallis channel as it cuts through the arid, pockmarked landscape.

The 1,300km-long channel winds from the highlands of Xanthe Terra through the lower plains of Chryse Planitia, before curving back onto higher ground. Scientists believe this huge channel was carved out around 3.5 billion years ago, when vast quantities of groundwater rushed downhill across the planet. It gouged out the immense valley system we can now see.

As you move over the channel, viewers can see the pockmarked landscape surrounding it, created by countless space rocks smashing into the Red Planet. The flight concludes with a spectacular view of the Da Vinci impact crater, a 100km-wide basin that contains a smaller crater within it.

The video is built entirely from data gathered by ESA’s Mars Express spacecraft, which has been orbiting the Red Planet for the past 20 years. Using its High Resolution Stereo Camera, the Mars Express has been steadily mapping the Martian surface in extraordinary detail, while also studying the planet’s atmosphere, geology, and even its tiny moon, Phobos.

To create this “virtual flight,” researchers created an image mosaic from the observations taken during a single orbit by the Mars Express. They then rendered them with a digital terrain model to produce a 3D view of the planet. Every single second of the film consists of 50 individual frames that have been rendered following a predefined camera path.

The video allows you to fly over Mars’ incredible landscape and imagine what our planet might have looked like billions of years ago.

Once thought of as just another icy satellite, Enceladus -- one of Saturn's 274 moons -- is now considered one of the few places in the solar system that might be able to support life. New evidence from NASA’s Cassini spacecraft has shown that Enceladus holds even more organic compounds than we previously thought. The complex molecules suggest this frozen moon could be habitable, maybe not by humans but by some form of life.

The researchers point out that this doesn’t mean the moon has life, just that it is theoretically possible. Organic molecules are the carbon-based compounds that all living things require. Finding them here shows it has at least some of the raw ingredients to sustain life. 

Geyser dust

The Cassini spacecraft spent 13 years orbiting Saturn before its dramatic end in 2017. Mission controllers deliberately plunged it into the planet’s atmosphere, with its onboard Cosmic Dust Analyzer. The device analyzed minuscule grains ejected from Enceladus’s geysers -- the jets of ice and vapor that spew from cracks near the moon’s south pole.

Some of these grains were older particles that had drifted into Saturn’s outermost rings. Other, younger grains were blasted out at far higher speeds. They collided with the piece of equipment at speeds of over 64,000kph. The high-speed collisions allowed scientists to look more closely at the grains’ chemical makeup. 

Alongside molecules already identified from older samples, there were new, more complex organic compounds not previously seen -- esters, alkenes, and ether compounds. Both esters and ethers are needed to form lipids, which are essential to life.

"We are confident that these molecules originate from the subsurface ocean of Enceladus, enhancing its habitability potential," lead author Nozair Khawaja told the CBC.

Beneath its icy crust, Enceladus has a vast saltwater ocean. After using data from Cassini to prove that the ocean exists, researchers have been scouring it to try to identify the various elements and compounds needed for life.

"Having a variety of organic compounds on an extraterrestrial water world is simply phenomenal," study coauthor Fabian Klenner told the Associated Press.

Giant underground lava tunnels have been discovered on Venus, our inhospitable, cloud-wrapped neighbor. Their huge size is peculiar and has forced scientists to discard their pet theories on how planetary lava tunnels form.

The surface of Venus is unlike Earth’s in nearly every respect. Those thick clouds that hide a direct view of its surface are made of sulfuric acid. The planet's temperature is around 460˚C, its atmospheric pressure is 93 times higher than ours, and it has more volcanoes than any other planet.

With these hellish conditions, you might think huge lava tunnels tie in quite nicely, but their size has baffled scientists. Lava tubes on Earth form when the outer layer of lava flowing beneath the surface cools and solidifies, while the interior remains molten. The molten lava continues to drain away, leaving behind a hollow underground channel. Our lava tubes are relatively modest in size because Earth’s gravity pulls heavily on the overlying rock.

On the Moon and Mars, the lower gravity has allowed lava tubes to grow larger without collapsing. The assumption has long been that weaker gravity results in larger lava tubes. So the discovery of huge lava tunnels on Venus, where the gravity is quite similar to Earth’s, turns that rule completely on its head.

“Earth lava tubes have smaller volumes, Mars tubes have slightly bigger volumes, the Moon’s tubes have even bigger volumes...and then there's Venus, completely disrupting this trend, displaying very, very big tube volumes," lead author Barbara De Toffoli told the Europlanet Science Congress earlier this month. "There's likely something more on Venus playing a significant role.”

Lava tubes leave surface hints

Scientists have long suspected the existence of lava tubes on Venus. Pits on the surface indicated they might exist. De Toffoli and her team discovered the unusual tunnels using radar imagery and mapping data from past Venus missions. They analyzed the surface pits and depressions near volcanoes and noticed patterns characteristic of collapsed sections of lava tubes.

Many of the pits also line up perfectly with the steepest section of volcano slopes where lava would have flowed, and the ratio of depth to width is consistent with the geometry of collapsed tubes.

Why these tunnels are so large remains a mystery. The leading theory relates to Venus's surface hellscape. The crushing pressure and extreme temperatures might cause lava to flow and solidify differently than elsewhere.

“Due to the very high pressure, there's an overall flattening out of the tubes, instead of having a very intense erosion at the floor that usually happens on other planets,” suggests De Toffolii.

Shelter from radiation

On the Moon and Mars, scientists have been eyeing the lava tubes as shelters for future missions. They serve as natural shields against radiation and harsh surface extremes. On Venus, surface missions are even more challenging due to the brutal heat and pressure. But these underground tunnels might someday offer some refuge for rovers and robotic probes. However, before anything like that can happen, we need to learn more about the lava tubes.

Future missions like ESA’s EnVision, scheduled to launch in 2031, will map the vast tunnels. The project will also have a subsurface radar sounder to detect the hidden cavities hundreds of meters underground. This should let scientists confirm the depth and geometry of the lava tunnels.

Astronomers have found a space rock that has been quietly hanging around Earth for decades: a tiny asteroid named 2025 PN7. This so-called “quasi-moon” isn’t a true moon or a mini-moon, because it orbits the Sun rather than our planet. But its orbit is so similar to Earth's that it will be our companion for around another 60 years.

Though the quasi-moon orbits the Sun, it occasionally looks from our vantage point like it is looping around us. However, our orbits are slightly different, so sometimes it lags behind us and sometimes it seems to lead us. But since the little asteroid's orbit around the Sun is very close to one Earth year, it is always pretty close.

2025 PN7 is just 19 meters across and might be the smallest quasi-moon ever found. Its minuscule size means that it can be quite tricky to spot. As astronomers put it, its "visibility windows" are very narrow. We can only see it through very large telescopes when its position and the lighting are favorable. That’s partly why it evaded detection for so long.

Entered orbit in 1957

Although the Pan-STARRS1 telescope in Hawaii discovered it in August 2025, the quasi-moon has been in this orbit for far longer. When researchers later trawled through archived images, they found that 2025 PN7 had shown up decades earlier. They think it likely entered its current orbit in 1957.

It won’t stay with us in this dance forever. Simulations suggest that it will keep up company for another 60 years before it wanders off in another direction. In that time, its distance from Earth will change quite a bit. So far, it has varied between 4 million kilometers at its closest and 18 million kilometers at its furthest.

2025 PN7 is one of seven quasi-moons in Earth-like orbits, and seems to be the smallest and least stable. Astronomers aren't exactly sure where it came from. It does not pose any threat to us.

"These asteroids are relatively easy to access for unmanned missions and can be used to test planetary exploration technologies [relatively cheaply]," said Carlos de la Fuente Marcos, lead author of the study.

Conventional images of the Earth and the moon place them close together, the moon hovering, seemingly, right over our planet's shoulder. Of course, this isn't accurate; we know just from looking at the moon in the sky that it isn't nearly so large or close. But every image of the Earth and moon, and of the solar system in general, is out of proportion.

To Scale's short film The Solar System opens by laying this out and asking the viewer if they've noticed it.

Wylie Overstreet, the man on camera, has noticed. Taking it a step further, he concludes that "the only way to see a scale model of the solar system is to build one."

Building the solar system to scale

The project takes Wily to Nevada's Black Rock Desert with his friend and cameraman, Alex. They start setting up, laying vast circles over seven miles of desert. It takes that much space to make a scale model using a marble-sized Earth. By chasing lights around the orbits at night and filming from an overlooking mountaintop, they hope to give an accurate idea of the scales involved, from above.

To check proportions, Alex stands with the camera at mini-Earth's orbit while Wiley raises the meter-and-a-half-wide sun. Then, they wait for the (actual, full-scale) sun to rise. Its size exactly matches the model, standing from the perspective of "Earth." Their math was right.

It makes for a fascinating visual display. But the point of the project wasn't just a matter of proportion. Wiley reminds us that only a few dozen people have gotten to see the entirety of Earth from space. Onscreen, old footage plays of a few of them, describing how it felt to see the Earth so small and distant. They use different words but all describe the same sight: the Earth, "all you've ever known," as small as, well, a marble.

By depicting the solar system to scale, Wiley's goal was "to try and capture [that] we are on a marble, floating in the middle of nothing. When you...come face to face with that, it's staggering."

Named 3I/ATLAS, this comet is the third-ever interstellar visitor to our solar system to be observed by astronomers. By the end of this month, it'll pass behind Mars and be blocked from our view, reemerging in December. Somewhere between 5.6 kilometers and 320 meters across, 3I/ATLAS is traveling at 209,000kph. That's fast enough to go from Earth to the moon in about an hour and a half.

For most astronomers, the chance to observe 3I/ATLAS is an opportunity to better refine our understanding of the objects that pass through our solar system. But for one controversial Harvard physicist, it represents something more: intelligent extraterrestrial life.

An alien emissary?

Avi Loeb, a somewhat notorious Harvard science professor, was quick to jump on the story of 3I/ATLAS. Only days after it was first sighted, he was questioning whether it was a comet or "something else." Two weeks after finding out about it, he released a preprint (meaning it has not been formally published or peer reviewed) paper. Raising the possibility that the comet was alien in origin, he outlined several key points.

These points included the fact that the orbital plane of 3I/ATLAS was very close to Earth's, within five degrees, which he felt was an astounding coincidence. Second, the object seemed to be extremely large, over 20 kilometers in diameter, which is vanishingly rare for a comet. There was also the fact that it was going to pass near Venus, Jupiter, and Mars, which he again cited as an unlikely coincidence. Finally, he claimed that there wasn't good evidence for the cometary gas trail we expect from a comet.

Relying on the "Dark Forest" solution to the famous Fermi Paradox, Loeb has gone on to suggest that the intelligence behind 3I/ATLAS may be malicious and planning on targeting Earth. Its path worked out so that it would pass behind the sun, hiding it from Earth, and at the exact point where it could use the Sun's gravity to swing back around toward Earth, presumably to destroy us all.

For months, he's been publishing blog posts on Medium almost daily, outlining his theories as more information comes out about 3I/ATLAS. But other astronomers, and now NASA, have come out with information debunking his theories.

An interesting exercise

Even Loeb himself is unwilling to commit to his theory. In the recent paper, Loeb et al claim to "not necessarily ascribe," to the theory, but feel it is "an interesting exercise in its own right, and is fun to pursue."

He also pursued this exercise in 2017, when he claimed that 'Oumuamua, the first confirmed interstellar object to enter our solar system, was possibly of artificial origin. He tasked radio astronomers with watching for alien signals coming from the object. They did, and there weren't.

Three years before that, Loeb thought a meteor entering the atmosphere could be the wreckage of an alien spaceship, citing seismic data he gathered from the crash site. Last year, planetary seismologist Benjamin Fernando led a team that found the cause of the odd readings. It was a truck driving by the sensor.

In a follow-up interview with The New York Times, Fernando said the two takeaways were "One, if you want to do seismic analysis, it’s ideal if you check with a seismologist first. The other is, it’s not aliens."

Point one goes a long way in explaining why Loeb's "interesting exercises" have received so much skepticism (and outright derision) from his fellow astronomers. Loeb isn't actually an expert in any of the science he's doing. Astronomy is a big field, and a man who is (like Loeb) a scholar of galaxy dynamics may not be qualified to speak on, say, comets.

Once respected within his field, Loeb's papers now mostly remain in preprint, with colleagues like Professor of Astrophysics Steve Desch saying that Loeb is "conflating the good science we do with this ridiculous sensationalism and sucking all the oxygen out of the room."

If it looks like a comet and quacks like a comet

The more we find out about the comet, the more absurd and hasty Loeb's claims become. For one thing, it isn't nearly as large as Loeb claimed. Observations from the Hubble telescope now show that 31/ATLAS is somewhere around, or smaller than, 2.8 kilometers. A far cry from Loeb's 46 kilometers. In fact, Loeb himself cited the paper which showed it's 2.8 kilometers, and simply... chose to ignore that.

As on the previous occasions, other astronomers were unimpressed with the science behind Loeb's bold theory. Steve Desch called the paper "sloppy work beneath the level of an undergraduate" and graded it accordingly.

Sorry it took me so long to grade your August 20 assignment, Avi Loeb. Are you sure you're ready for a class on comets? You might need to learn about things like bow shocks and chemistry.

[image or embed]

— Steve Desch (@deschscoveries.bsky.social) 9 September 2025 at 20:20

The comet does have interesting properties. It comes from outside our solar system and may have a different chemical composition than we're used to seeing. But as Tom Statler, NASA's lead scientist for solar system small bodies, told The Guardian, "It looks like a comet...It does comet things. It very, very strongly resembles, in just about every way, the comets that we know. It's a comet."

To Loeb's argument that 3I/ATLAS brightens strangely, Statler agreed -- because it's normal for comets to do that. Even ones from within our solar system can react unpredictably as they grow closer to the radiation of the sun. Comets are mostly ice, and the heat of the sun melts chunks of ice, causing changes in size, brightness, and composition.

It isn't merely boring alien haters bashing on the visionary who dares to dream the impossible dream. Many of the scientists criticizing Loeb's work are from institutes like SETI, which is dedicated to the search for extraterrestrial life. They feel that Loeb's attention-grabbing, unsupported claims discredit the whole field, making it harder to do actual science.

You can follow the comet's path live on NASA's website.

Where is the true "middle of nowhere?" Philosophically speaking, it's always about two hours drive from your home town. Scientifically, it's Point Nemo: a place which is important due to the immensity and scale of its unimportance.

A deep blue spot of nothing located roughly 48°52.6′S x 123°23.6′W, Point Nemo is the farthest point on Earth from any landmass. It's also the future tomb of the International Space Station.

The Pole of Inaccessibility

Point Nero is the oceanic Pole of Inaccessibility, the solution to the "longest swim problem." This problem presented the challenge of finding the point on earth where, if one fell over the side of a ship, they would have to swim the longest possible distance to reach any land.

The solution came from Czech engineer Hrvoje Lukatela, who published his findings in 1992. By mathematical necessity, the Pole of Inaccessibility would have to be equidistant between three or more coasts. If one piece of land were further away than the others, then the swimmer could head for one of the two closer islands and would therefore not be completing the longest possible swim.

Using software he himself developed, combined with the only dataset of coastlines then available, Lukatela found what he would come to call Point Nemo. The three vertices are Ducie Island, of the Pitcairn Islands, Motu Nui, an islet off the more famous Rapa Nui, and Maher Island in Antarctica.

Lukatela named the point for Captain Nemo, meaning "no one", from Jules Verne's 20,000 Leagues Under the Sea. The book was one of his favorites. Lukatela further explained in a 2015 interview that because Nemo "vowed to...never to set his foot on dry land again," his name "seemed to me to be appropriate for that point on the world's oceans that is most distant from any land."

In 2022, he ran the calculations again using newer, more accurate data. The three vertices were the same, but everything had moved by a few kilometers. The Point Nemo of today, at around 48°52.6′S x 123°23.6′W, is slightly off from the Point Nemo of the 2000s. But when you're aiming from space, a few meters here or there don't mean much.

Where do we put our space trash (other than space)

You're probably aware that we've been putting a lot of stuff up in space over the past seven decades or so. We now have quite a lot of stuff up there and are beginning to realize we may have been a bit intemperate with the practice.

The European Space Agency is tracking 40,230 man-made objects currently in low earth orbit (LEO). Others too small to track number somewhere in the hundreds of millions. The knock-on effects are substantial. Debris can damage spacecraft or cause destruction when it falls to Earth. NASA estimates that we've had an average of one piece of junk per day falling to Earth over the last 50 years.

It's a problem that requires creative solutions, like the wooden satellite designed by Japan's Aerospace Exploration Agency. Various global agencies have also considered (and even tested) harpoons, nets, robots, and lasers.

Then there's the related problem: When we bring old crafts and satellites down, where do we land them (considering "land" is the polite word for "crash")? Well, the farthest possible spot from anywhere else, obviously. Point Nemo has been a satellite graveyard for decades.

In fact, we've dumped nearly 300 satellites, manned and unmanned, into the point's general area over the past 50 years. This includes the progenitor of the ISS, Mir. 

Tomb of the ISS?

In recent years, NASA has been handing over the reins to near-Earth space to private companies, most notably SpaceX, in order to focus on more distant exploration. Also, after 24 years, everything on it is getting pretty old and broken and would be a real expensive hassle to replace.

The execution date is set for 2031. The place? The middle of nowhere.

Given its history and properties, Point Nemo was the obvious choice for de-orbiting the International Space Station. In fact, the ISS and Nemo have something of a history already. When the ISS passes over Nemo, it becomes the nearest human habitation. Point Nemo is so isolated that it's closer to the space station than to anywhere else.

"The fish probably don't enjoy having space garbage rained on them," you say. Apparently, though, fish don't hang out at Point Nemo either. This area, lying within the South Pacific Gyre, has such low productivity that scientists have called it an oceanic desert.

Still, ocean pollution travels. There is a degree of concern, especially since some of the material being dumped is radioactive. The Point Nemo graveyard plan isn't a perfect solution; it's more like harm reduction.

The Rock and Roll with NASA competition offers up to $155,000 in prizes for innovative lunar wheel designs. In two-and-a-half years, NASA is planning its next manned mission to the moon. With them will be a lunar terrain vehicle (LTV). 

The tires that carried Apollo astronauts across the lunar surface in the 1970s tripled their exploration range. But they were designed to survive just a handful of slow, careful drives. The Artemis program needs something far more advanced.

These tires will ferry cargo between South Pole landing zones and work sites kilometers away. They will need to tackle 20-degree slopes, rugged terrain, extreme temperatures, and months of use at higher speeds.

To find a new design, NASA is calling on engineers and innovators around the world to come up with ideas.

“NASA is returning crews to the Moon to establish an enduring, science-driven presence that will serve as the springboard to Mars,” it announced. "Central to that ecosystem is mobility...Innovation in mobility will be key to maximizing exploration."

The challenge is to create wheels that can withstand the moon’s terrain while also traveling five times faster than the Apollo rover did.

"Rigid wheels work for slow, careful driving, but they struggle at higher speeds to absorb impacts as obstacles are traversed," NASA explained.

It is looking for novel wheel concepts that combine low mass, shock absorption, and long life in a harsh environment.

Three phases

The contest has three phases. Phase one will see competitors submit a 3D CAD model of their wheels. They must also include a seven-page report explaining their design and how it meets the needs outlined by NASA. The deadline for this is November 5. A panel of experts will judge these entries and choose up to 10 for phase two.

Phase two will take place from January to April 2026. Entrants will need to produce a prototype of their lunar wheel and a video of its assembly and testing process. From here, a maximum of five teams will progress to the final phase. They will have to demonstrate their wheel’s capabilities on the MicroChariot Rover at NASA’s Johnson Space Center Rockyard in Texas.

By summer 2026, NASA expects to crown a winner after subjecting the top designs to performance and durability trials. For many participants, the reward is not just the prize money, but the chance to leave a mark on the future of space exploration. Though there can only be one winner, any wheel designs that show promise will be shared within NASA for potential use in other missions. 

Space is packed with hazards and health risks, and researchers have spent decades discovering what space travel does to the human body (answer: nothing good). But a new study suggests that the effects are more fundamental than we realized. Spending time in space can actually speed up the physical aging process on a cellular level.

Cells in space

The recent study, funded by NASA and conducted by the University of California San Diego's Sanford Stem Cell Institute (UCSD), examined the effects of space travel on human stem cells.

Specifically, these were human hematopoietic stem and progenitor cells, or HSPCs. Stem cells are cells that are not yet fully differentiated, meaning they can become various types of cell. HSPCs can become blood cells and are an important part of the immune system and vascular health.

SpaceX periodically sends craft to the International Space Station on resupply missions. For this experiment, the UCSD team, led by Dr. Catriona Jamieson, sent some cells up with them. The scientists cultured the cells inside a "nanobioreactor" of the team's own invention. The nanobioreactor kept the HSPCs in a stable environment and monitored a number of important health indicators.

The cells spent 32 to 45 days in space across several different supply missions. Once they got home, researchers compared them to a control group that never left Earth.

Cells hate being in space

The cells that went to space came back changed. They were more vulnerable to mutations, were less able to make new, healthy cells, and were losing their DNA protection more quickly.

In some ways, their findings corroborated earlier findings. Most importantly, the famous "twins study," where astronaut Scott Kelly went to space while his brother Mark stayed home. The stem cell study confirmed what the Kelly brothers demonstrated: Space is bad for telomeres.

Telomeres are a protective cap at the end of your DNA. When DNA is copied, a little bit at the end is chopped off. The telomeres get chopped off first, so you don't lose anything important -- until you run out of telomeres. Scientists believe that losing your telomeres is an important element of the aging process. It seems that space travel inhibits telomere maintenance.

Exposure to damaging ionizing radiation in space also made the cells more likely to mutate. We've been aware of possible increased cancer risks for astronauts for a long time, but this new evidence will help provide direction for future research.

The cells showed broader signs of stress, wear, and aging as a result of space. The mitochondria (the powerhouse of the cell) exhibited stress responses, which could decrease immune health. The cells became more active, burning through stored-up energy, inhibiting their ability to recover.

Good news for the HSPCs (and space enjoyers)

It isn't all bad news. The research team kept monitoring the cells after they returned to Earth and found they showed signs of recovery. After spending 12 days cultured on healthy young bone marrow stromal layers, the cells were perking up and increasing their capacity for self-renewal.

This data confirms at a cellular level much of what the twins study suggested. Once Mark Kelly returned to Earth, many of the negative effects of time in space reversed, at least partially. But, as the study's authors warn, the effects of longer-term space travel may be more dramatic and more permanent.

As we continue to send people to space, we'll need research like this to better understand how to protect astronauts from the physical consequences. As Dr. Jamieson said in a UCSD press release: "This is essential knowledge as we enter a new era of commercial space travel and research in low Earth orbit."

Beneath the surface of Mars lie an array of mysterious "blobs" that might hold clues about the earliest days of our solar system. NASA's InSight Lander discovered the dense lumps scattered through the planet's mantle.

Marsquakes

From 2018 to 2022, the InSight Lander monitored and recorded data from 1,319 marsquakes. These quakes produce seismic waves, which change slightly as they move through different materials. Astronomers sought the data to study the planet's interior structure, and have been able to determine the depth and composition of Mars’ crust, mantle, and core.

While analysing the data, researchers noticed that in some of the marsquakes the seismic waves exhibited unusual behaviour. They were slowing down, hitting dense blobs of material in the mantle. Some of these mysterious blobs were huge, with widths up to 4km.

"When we first saw this in our quake data, we thought the slowdowns were happening in the Martian crust," co-author of the new study, Tom Pike, said in a statement. "But then we noticed that the farther seismic waves travel through the mantle, the more these high-frequency signals were being delayed."

Early impacts

Researchers think that objects crashing into Mars during the early days of the solar system created the blobs of dense material.

"What we’re seeing is a mantle studded with ancient fragments," lead author Constantinos Charalambous explained. Mars does not have tectonic plates like Earth; the movement of tectonic plates constantly recycles our crust and upper mantle. On Mars, this doesn’t happen. Mars has one single plate, which means there is much less activity, and this is what allowed the lumps to form.

"These colossal impacts unleashed enough energy to melt large parts of the young planet into vast magma oceans," explained Charalambous. "As those magma oceans cooled and crystallised, they left behind compositionally distinct chunks of material, and we believe it’s these we’re now detecting deep inside Mars."

A solid inner core

That was not the only discovery revealed this week. Analysis by a team of Chinese and American scientists revealed that the planet appears to have a solid inner core. This upends previous assumptions.

Seismic data from InSight suggests there is a 600km-wide solid mass at the centre of the planet. "Our results suggest that Mars has a solid inner core making up about one-fifth of the planet’s radius, roughly the same proportion as Earth’s inner core," lead investigator Daoyuan Sun said.

As light pollution threatens our view of the stars the world over, the annual Dark Sky photography contest is here to remind us what we stand to lose.

DarkSky is a non-profit that works to help preserve astronomical heritage and nighttime ecology. In their photography competition Capture the Dark, they reward not only photographs that capture the majesty of dark skies, but also host categories such as dark sky-friendly lighting, the impact of light pollution, and nocturnal flora and fauna. Thanks to funding from local governments, special prizes also go out to photographs shot in Utah and Tucson, Arizona.

Beauty in darkness

The overall prize this year goes out to a split-second photograph of red sprites over Australian tidal flats. Red sprites are a rare form of lightning seen during thunderstorms. Unlike the more common tropospheric lightning, which occurs at the base of the atmosphere, red sprites last only about 10 milliseconds. Their short duration makes them notoriously difficult to photograph.

Another winner in this category depicts a swathe of white snow beneath the southern Milky Way. A small cabin stands in stark, man-made dichotomy beside the peak of a volcano. On the ground, a trail of footsteps mirrors the glowing lights of the galaxy above.

International Dark Skies

Many entries in this competition tempt viewers into buying a plane ticket to New Zealand, but perhaps none so much as the winner of the International Dark Sky Places category. Officially inaugurated in 2012, the Aoraki Mackenzie International Dark Sky Reserve stretches across several national parks. The first-place winner of this category documents the entry to the park.

Another photograph showcasing the Aoraki Mackenzie International Dark Sky Reserve made it to the podium as well. Flowers dance beneath star trails, all against the backdrop of the Church of the Good Shepherd.

How to build for dark skies

There are many steps urban planners can take to reduce light pollution. The first place winner in the category Dark Sky Friendly Lighting and Design is a gentle cityscape of Paris in the hours before dawn. The City of Lights will never be a stargazer's dream. But Paris turns off the lights on many of its most prominent landmarks late at night, allowing some stars to peek out of the firmament.

Warmer, redder lights also help reduce light pollution. Because blue light scatters more easily off the atmosphere, it travels farther from its origin. Red light is also less energetic, so it leaves less of an imprint on your retina, allowing you to preserve night vision. And crucially for local ecology, red light attracts fewer insects and birds than other colors.

As a bonus, it gives any building a nice cyberpunky feel, as shown in the second-place winner in this category.

Light Pollution

The light pollution category is here to dispel any hopeful feelings you're having about humans' ability to diminish their natural impact. Fortunately, the prize winners in this category make light pollution as striking as dark skies.

First place goes to a mountainscape above Chamonix. Despite the glittering stars above, the lights from the town below travel up through the fog bank, glowing like a lamp.

Two photographs from major Chinese cities take second and third place, documenting very different aspects of light pollution. In the second-place photograph, the skyscrapers of Shanghai far outshine a few sparse star trails above.

The third-place winner, taken in Beijing, documents not the impact of the city but the constellations of satellites above. The Pinwheel Galaxy shines against a star-speckled sky crisscrossed by satellite trails.

Creatures of the night

Darkness serves a crucial ecological purpose. This category spotlights the flora and fauna that flourish at night, from fungi to insects and birds. Particularly striking is the third-place winner, a close-up portrait of an owl in the Sonoran Desert:

Deep-sky images

No astrophotography competition is complete without a deep-sky category. The first-place winner shows the Vela supernova remnant. Made from a whopping 109 hours of integrated observations, this photograph consists of different colors highlighting layers of oxygen, hydrogen, and silicon.

Visit Tucson Location Award

As a former resident of Tucson, Arizona, I'd be remiss to leave out my favorite from the Visit Tucson location award. Thanks to the City of Tucson for funding this charming photo entitled Two Lovers Watching the Moonrise:

Take a look at the other winners!

You can find out more about the importance of dark skies and how to preserve them here. The rest of the Capture the Dark 2025 winners are here.

Fast-than-light travel, instantaneous communication, terraforming. Science fiction relies on imaginative physics ideas to enrich its stories. Some of these are pure fiction, while others are closer to fact than you might expect. Which is which?

Faster-than-light travel probably won't work

Perhaps no concept is more foundational to modern space fiction than that of faster-than-light (FTL) travel. After all, exploring a galaxy even at lightspeed takes prohibitively long for any narrative. In the time it takes the Enterprise to travel to a new planet each episode, any characters not on the ship have aged and died.

The proposed mechanics of FTL vary across sci-fi properties, but many authors (George Lucas, Douglas Adams, Martha Wells, CJ Cherryh...) use the vocabulary of wormholes and hyperspace. Both of these refer to real, physical solutions to Einstein's equations.

In fact, many physicists suspect that if we fully understood gravity, these solutions would be impossible. Einstein's equations fail to describe gravity at the atomic scale, for example. A theory that encompasses quantum gravity as well as macroscopic gravity might make wormholes impossible.

Right now, though, Einstein's equations are the best we have. And while they allow wormholes, further calculations suggest that it's probably impossible to travel through them. This might be a good thing, considering the eldritch horror of getting stuck in hyperspace, as depicted in CJ Cherryh's haunting sci-fi novel Port Eternity, where a spaceship drifts forever through hyperspace darkness while unknown creatures knock on the walls.

But there is a property that uses an FTL mechanism closer to reality: Star Trek. In fact, physicist Miguel Alcubierre cited Star Trek in his seminal paper on an object now known as an Alcubierre drive. This shortens the space in front of a ship in the same way gravitational waves do. With an Alcubierre drive, a spaceship doesn't actually move faster than light, and so doesn't violate any laws of general relativity.

The catch? How to make a machine that can contract and expand spacetime. Alcubierre showed that it fits mathematically into Einstein's laws, but only if it uses matter with negative mass as fuel. Right now, most physicists suspect such peculiar matter does not exist.

Still, Star Trek gets closer to feasible FTL than most other sci-fi properties. Take that, Star Wars.

FTL communication is also a no-go

Very few pieces of space fiction depict worlds without faster-than-light travel. The first book in the peculiar Bobiverse novels, whose major characters are all clones of one human-turned-AI, does show its protagonist colonizing the universe without FTL, but the process takes centuries. In Cixin Liu's novel The Three Body Problem (now a Netflix series), humans buy precious time to prepare for an alien invasion thanks to the aliens' sub-light travel speed. And in the early Ender's Game novels, the eponymous Ender spends enough time on sub-light spaceships that he's still alive 2,000 years after the first book, thanks to time dilation — at which point he is universally reviled.

All of these authors, though, cave on the point of FTL communication. Despite the laws of physics being just as firm on superluminal Zoom as they are about superluminal spaceships, the allure of real-time conversations seems too much for science fiction authors not to take advantage of.

When authors try to work in FTL communication, they often appeal to the phenomenon of quantum entanglement -- where particles become linked together so that they share the same fate, no matter how far apart they are. Entanglement is so bizarre that Einstein, in the throes of his philosophical war on quantum mechanics, famously called it "spooky action at a distance."

Quantum mechanics predicts that two particles can be connected so that any measurement of one also tells you the state of the other. For instance, imagine an atom with zero intrinsic angular momentum, or spin, decays into two smaller particles. We measure one of them and find that it's spin points in the upward direction. Since we started with no spin, we know that the other particle's spin has to cancel this out. It must have a downward spin.

The pioneer of quantum photonics, John Stewart Bell, described entanglement in reference to a quirky coworker of his, Reinhold Bertlmann. "Dr. Bertlmann likes to wear two socks of different colors. Which color he will have on a given foot on a given day is quite unpredictable," wrote Bell, in an excellent and accessible essay on entanglement. But when you see, illustration below, that the first sock is pink, you can already be sure that the second sock is not pink."

Bertlmann's socks, of course, are simpler than quantum entanglement. If you turn around and give his socks a moment, they won't randomly switch color. Quantum systems, though, do. You can measure one decayed particle at 9 am, find that it has a downward spin, and then come back after lunch only to find its spin has switched direction. The one thing you know is that at each point, the other particle will have the opposite spin.

It's surprisingly easy to test this in a lab. Entangled photons and electrons are bizarre, but totally real. Physicists have even managed to entangle millimeter-sized diamonds.

If whatever happens to one particle affects the other, Einstein reasoned with skepticism, then wouldn't entanglement allow FTL communication? For instance, the pure act of measuring a quantum system collapses it into a classical system, without all the mucky probabilistic behaviors of quantum.

Say the Greek hero Theseus has one half of an entangled quantum system and gives the other to his father. They agree that if Theseus survives his fight against the Minotaur, he will measure his half of the system, thereby collapsing the half in the care of his father into a classical system as well. The transfer of information is instantaneous. Theseus enacts spooky action at a distance.

But there's a problem. In order to check whether his half of the entangled system has collapsed, Theseus' father has to measure it. Doing so would collapse it. His father has no way of knowing whether Theseus' observation or his own has changed the system. No matter what, it looks as though Theseus lives. This goes to show that if the ancient Greeks had only had quantum theory, everything would have turned out all right for Theseus' father.

Collapsing a quantum state is only one of many proposed mechanisms for FTL communication via entanglement. But the "no-signaling theorem," provable with relatively simple mathematics, outlaws all of them. The very act of measurement breaks the entanglement, and each half of the system joins its surrounding environment, independent of the other half. Trying to communicate across quantum entanglement is like sending a letter via a beautiful, fast carrier pigeon that happens to drop dead if you tie anything to its feet.

Terraforming is not instantaneous

In Star Trek II: The Wrath of Khan, the enigmatic antagonist searches for a terraforming mechanism called the Genesis Device, which remakes planets in minutes. No such device exists, and no serious physicists or biologists propose to make one.

But the idea of turning a lifeless planet into a life-bearing one does have legs. The core questions of astrobiology are: How does life form, and how rare is it? Research on these topics naturally leads to the suggestion, either as a thought experiment or a policy proposal, that we attempt to create it ourselves.

We've reported before on proposals to breed specialized microbes capable of surviving on Mars and eventually giving rise to algae. But perhaps the biggest barrier to Martian terraforming relies not on biologists but on physicists to solve it. Life on Earth only exists because of our planet's magnetic field, and Mars has none.

Every second, tens of thousands of dangerous particles pummel our atmosphere. Called cosmic rays, these particles -- primarily electrons and light atoms -- originate in the Sun, in the explosive deaths of stars, and even in distant black holes. Their births are violent. They accelerate to nearly the speed of light and shoot through anything in their way like a bullet.

That includes human cells. But fortunately, the Earth's magnetic field gently ushers cosmic rays to the Poles, where they either cascade down to Earth or join the solar wind. Unless you're a researcher at the Amundsen-Scott South Pole Station, you don't have to worry about cosmic rays.

But you would on Mars. So would any hopeful plant life trying to get a foothold on the red planet. Physicists, however, are already tackling the issue of an artificial Martian magnetic field. One team found that "the most feasible design is to encircle Mars with a superconducting wire with a loop radius of about 3,400 km" and running a current through it to create a magnetic field. Making this wire would only require mining 0.1% of Olympus Mons(!)

Both the microbial and the magnetic components of terraforming are potentially feasible. But neither one is the instant Genesis Device from Star Trek. Granting algae a toehold on Mars would take decades, and full-fledged forests would come centuries later. And no matter how we would create a magnetic field for a planet, it would take massive amounts of labor.

Real-life terraforming

Terraforming research has picked up in recent decades, as climate change looms ever-larger in the minds of many scientists. It's tempting to hear the phrase, "There is no Planet B," and ask: But what if there was?

There could be. But terraforming a new planet, while feasible, would be slow and painstaking.

In fact, terraforming is already occurring in small controlled experiments on Earth. Scientists have begun using salt-based aerosols to deflect sunlight. After successful tests, one team has even begun using them over the fragile, floundering Great Barrier Reef.

Experiments like these are deeply controversial but are gaining traction as the effects of climate change become more apparent.

Solar-deflection aerosol engines look like something out of the planet-creation scene in The Hitchhiker's Guide to the Galaxy. But they're real, and unlike in Hitchhiker's Guide, they're happening on the only Earth we have.

Scientists using the James Webb Space Telescope (JWST) have discovered the oldest known black hole in the universe.

Nestled within a glowing red galaxy, it dates back 13 billion years and provides a rare glimpse into the universe’s earliest moments.

The black hole and the galaxy it belongs to are called CAPERS-LRD-z9. It is part of a series of galaxies known as the Little Red Dots. Compared to other galaxies, they are tiny, and they emit red light.

Since 2022, scientists have been puzzled by the red spots. Observed in the distant realms of our universe, astronomers thought they were either a cluster of faraway stars or black holes at the center of different galaxies. The fact that they emit so much light suggested that they might be clusters of stars. However, they formed at such an early time that so many stars together was improbable. 

A new class of galaxy

“We started seeing these objects everywhere,”  Anthony Taylor, co-author of the new study, told Science News. It is now generally accepted that the Little Red Dots are a new class of galaxy that formed in the early stages of the universe.

The team decided to focus the JWST on one in particular, which seemed to be the oldest. This was CAPERS-LRD-z9. It emitted a huge range of infrared wavelengths. Using spectroscopy to split the light, the team studied the wavelength characteristics, looking for the fingerprint of a black hole. 

As fast-moving gas is sucked into black holes, it circles and creates a certain pattern of wavelengths of light. The gases moving toward us stretch into red wavelengths, while those moving away compress into blue wavelengths.

“There aren’t many other things that create this signature. And this galaxy has it!” exclaimed Taylor in a statement. 

A blink of time

A few even more distant spots could potentially be older black holes, but researchers have yet to see the same spectroscopic signature from them. This means that, at the moment, this is the oldest black hole ever discovered. At 13.3 billion years old, it formed just 500 million years after the Big Bang -- a blink of time in the scale of the universe.

“When looking for black holes, this is about as far back as you can practically go,” said Taylor. "We’re really pushing the boundaries of what current technology can detect."

Though the galaxies are quite small, the black hole at the center of CAPERS-LRD-z9 is not. It is about 300 million times the mass of our Sun, and roughly 10 times more massive than Sagittarius A*, the black hole at the center of the Milky Way. Even more intriguingly, its mass might represent around half of its galaxy’s total stellar mass, a proportion far greater than in younger galaxies.

Studying CAPERS-LRD-z9 doesn’t just confirm the existence of a black hole. It gives astronomers a crucial testing ground to refine theories of early galaxy and black hole evolution.

“We only ever survey very tiny areas of the sky with the James Webb Space Telescope,” said co-author Steven Finkelstein, “So, if we find one thing, there’s got to be a lot more out there.”

Planetary scientists have published a detailed follow-up on the debris from their historic 2022 asteroid impact experiment in outer space. What they found challenges their understanding of the asteroid's behavior since the impact. Two tight clusters of boulders have veered off from the main zone of debris at very high velocities.

Those boulders have escaped the asteroid system and are now orbiting the Sun. It's unclear where on the asteroid they came from, why they're moving so differently from the rest of the debris, or what they mean for the long-term course of the asteroid.

A historic asteroid deflection test

In 2022, NASA live-streamed one of the most daring missions in its history. The Double Asteroid Redirection Test, or DART, sought to change the orbit of an asteroid by slamming into it with a spacecraft. The challenge was enormous. The size of the target asteroid -- named Dimorphos -- in the night sky is akin to a single atom held at arm's length.

The team behind DART knew they might be live-streaming their spacecraft missing the asteroid. But in an era of misinformation, conspiracy theories, and apocalyptic panic, they wanted the public to have transparency every step of the way.

Their gamble paid off. The DART spacecraft knocked smack into Dimorphos. NASA proved that in the event that a killer asteroid is heading towards Earth, we can knock it out of the way.

Strange boulders

DART was proof to the public that planetary scientists can keep them safe, but first and foremost, it was a scientific experiment. Simulating asteroid impacts on a computer doesn't compare to the real thing, especially when there are so many things about asteroids we don't know. They can be as chemically and topologically variable as terrestrial geology, and their tiny size makes observing them challenging.

So, to protect Earth from a hazardous asteroid, planetary scientists have mined every aspect of the DART mission for pieces of the puzzle. The new boulder tracking study, published this month in the Planetary Science Journal, uses images taken by an ESA spacecraft called LICIACube that accompanied DART.

The researchers found that two main groups of boulders veered off from Dimorphos in the minutes after impact. Many of them aren't following the main cloud of debris, and have such high velocities that they can escape the asteroid system.

The team's top theory is that these boulders are the fractured remnants of larger rock formations right next to the impact site. Since they were already loose, the spacecraft easily dislodged them before reducing them to smithereens.

Boulders mean orbital calculations might be off

None of these boulders is anywhere near large enough to threaten life on Earth. If they happened to head towards us, they would vaporize upon atmospheric entry, treating us to a spectacular meteor shower. But they are massive enough that, without accounting for them, planetary scientists may have been miscalculating Dimorphos' new orbit.

The theory of rubble and impacts has to catch up to the observations. How can we predict what kinds of debris will form from striking an asteroid? How much momentum do boulders account for? How do we figure out how boulder-prone an asteroid is before we get there? We need to understand all of this so we don't miscalculate how to strike an asteroid.

DART means that we get to figure this out now, rather than when the Earth is on the line.

The international team of astrophysicists behind the world's three gravitational wave detectors just submitted a paper analyzing a uniquely strong gravitational wave from 2023. Caused by merging black holes, this gravitational wave is unusual for more than just its strength. The team's best models suggest that at least one, if not both, of the black holes shouldn't exist.

The black hole "mass gap"

Most large black holes are created when massive stars jettison their outer layers. The iron core, no longer supported against gravity, collapses in on itself and forms a black hole. But this kind of supernova only works for stars up to about 130 times the mass of the Sun.

Above that, astronomers theorize that a new type of supernova takes over. The light the star generates in its core doesn't manage to exit the star itself. Instead, many of the photons are so energetic that they create extra particles when they hit atoms at the right angle. That means that the pressure of light holding up the star vanishes. With its only defense against gravity gone, the star begins to collapse, triggering a massive thermonuclear explosion that vaporizes it entirely. Nothing remains, not even a black hole.

Astronomers have yet to confirm this kind of "pair instability supernova" actually exists, although simulations suggest it does. There are also several candidate pair instability supernovae observations, but further study is needed to confirm them. On balance, though, pair instability supernovae are a well-supported theory of stellar evolution. They imply that stars can't create black holes above 64 times the mass of the Sun and below about 130 times the mass of the Sun. After that, a new kind of supernova takes over and can produce black holes once more.

But the best models of the 2023 gravitational wave predict two black holes of 103 and 137 times the mass of the sun. The error bars on these measurements are sizable, but still place the lighter black hole firmly in the mass gap, while the heavier one is either in or above it.

These are also the heaviest reliable black hole measurements to come out of the LIGO collaboration.

Spinning black holes create gravitational waves

Gravitational waves occur when massive objects accelerate, rippling spacetime in their path. Black holes spinning together in the final moments before their collision create the most powerful gravitational waves.

Earth-bound systems of lasers, able to detect changes in distance of only 1/10,000th the size of a proton, go after this class. The Laser Interferometer Gravitational-Wave Observatory (LIGO) detected its first gravitational wave in 2015, finally confirming their existence.

The many possibilities for formation

The research team found one other clue to the history of this strange black hole system. Each of the black holes is spinning much faster than usual. Any explanation for how this system formed has to explain that as well.

It's possible that there are toggles on stellar evolution, such as exact nuclear reaction rates at high densities, that change the range of the mass gap. But that doesn't explain the high spin rates. The theory of two stars combining to create each black hole has the same issue.

One explanation that accounts for the spin rates is that one or both of the black holes are the remnants of previous black hole mergers, rather than a collapsing star. Although this requires exotic star cluster conditions, the universe is filled with those. (The research team favors this explanation.)

The colliding objects could also be primordial black holes, a predicted population of black holes formed during the dense stages of the early universe. Primordial black holes don't have any mass gaps, but they are also far more theoretical than pair instability supernovae.

In 2035, the European Space Agency plans to launch the Laser Interferometer Space Antenna, or LISA. LISA will probe a different regime of gravitational waves from the Earth-based detectors like LIGO. In doing so, it will add a host of strange new black holes to the canon.

An otherworldly treasure is heading to the auction house this month. A massive piece of Martian rock will be sold at Sotheby’s, and experts think it will fetch millions.

Officially named Northwest Africa 16788 (or NWA 16788), it is the largest Martian meteorite ever discovered on Earth. We have only found 400 meteorites from Mars, and most are just small fragments. This weighs in at nearly 25 kilograms, which is 70% larger than the next biggest piece of Mars that has landed on our planet.

Researchers are unsure when it crashed into Earth, but it was found in the Agadez region of Niger, in the Sahara Desert in November 2023. It is believed to have broken off the Martian surface in a violent asteroid impact before drifting through space and eventually crashing onto our planet.

Research shows that the meteorite contains a large amount of magnesium and iron-rich crystals, and that some minerals within it have turned into glass. This is likely due to the original force of the asteroid impact and its subsequent journey through our atmosphere.

A $4 million rock?

Sotheby’s in New York will auction the meteorite on July 16, and it could make history. Experts estimate that it could sell for between $2 million and $4 million, potentially setting a new world record for a meteorite sold at auction.

“NWA 16788 is a discovery of extraordinary significance — the largest Martian meteorite ever found on Earth, and the most valuable of its kind ever offered at auction,” said Cassandra Hatton, vice chairman of science and natural history at Sotheby’s. "Weathered by its journey through space and time, its immense size and unmistakable red color set it apart as a once-in-a-generation find. This remarkable meteorite provides a tangible connection to the red planet."

The auction has also sparked debate. Some scientists worry that if the rock ends up in a private collection, its scientific value will be lost. Paleontologist Steve Brusatte expressed disappointment over the prospect, saying it would be a shame if the meteorite “disappeared into the vault of an oligarch” rather than being preserved in a public museum.

On the other hand, some experts are hopeful that a new owner could collaborate with researchers to unlock more secrets from Mars. Julia Cartwright, a planetary scientist at the University of Leicester, noted that “the scientific interest will remain,” regardless of who ends up buying it.

Before it’s sold to the highest bidder, NWA 16788 will be on public display at Sotheby’s from July 8 to July 15, giving space lovers and curious onlookers a rare chance to stand face to face with a real piece of Mars.

Yesterday, the ATLAS telescope identified a potential interstellar interloper. The memorably named A11pl3Z (kidding) is currently zooming toward the Sun. Right now, it's about the same distance from the Sun as Jupiter is. But the strange angle of its approach suggests it may be coming from interstellar space.

If confirmed, it would be only the third identified interstellar small body.

Small bodies encompass everything from dwarf planets like Eris to comets and asteroids. Only in the last decade have astronomers gotten good enough at tracking small bodies to find interstellar ones. Each new visitor tells us something about other solar systems, from the chemistry of their small bodies to their orbital conditions.

The first two interstellar visitors

In 2017, astronomers at the University of Hawaii found an asteroid that behaved oddly. It didn't come from any of the normal directions for asteroids or comets passing by the Sun. Moreover, it wasn't on a bound orbit at all. It was traveling so quickly that after half a loop around the Sun, it zoomed back off into interstellar space.

They called it 'Oumuamua, meaning "scout." It was the first known visitor from beyond our solar system. Planetary scientists jumped at the chance to study an asteroid from the great beyond. More excitable astronomers theorized it was actually a spaceship. 'Oumuamua entranced the world for a few months, stirred up controversy, and then disappeared into the blackness of space, beyond the reach of our telescopes.

Then, in 2019, an amateur astronomer and telescope-maker in the Crimea found a comet (a rocky body that contains large amounts of ice, unlike asteroids) on a similarly unusual trajectory. Like 'Oumuamua, Comet Borisov darted through our neighborhood only long enough to vaporize some of its ice in the heat of our Sun. Then it, too, was gone.

What we know about A11pl3Z

Astronomers have only just discovered A11pl3Z, and it's very faint. Since it doesn't generate its own light, we can only see it via reflected sunlight. At its current distance, that only gives it a brightness equivalent to that of galaxies about one billion light-years away.

This obfuscates exactly how fast A11pl3Z is traveling, and in what direction. While it's still possible that A11pl3Z is just a very odd object from our solar system, it looks very interstellar. Not only is it entering the solar system from a strange angle, it's also orbiting in the opposite direction from solar system bodies.

Right now, it seems less perturbed by the Sun's gravity than Oumuamua or Borisov. That means it came from outer space with a much higher velocity.

The study of small bodies moves very quickly. Every night, planetary scientists get a plethora of new information on interesting objects. Soon, we should know whether A11pl3Z is an unusual member of our own solar system or something from much further abroad.

A team of astronomers in Australia searching for radio flashes from distant galaxies has found something a lot closer to home. The defunct communications satellite Relay 2, out of commission since 1965, is chirping at the Earth in radio frequencies.

A mysterious burst from nearby

The Australian Square Kilometer Array Pathfinder (ASKAP) searches the radio sky for sudden, unexpected flashes. These can come from supernovae or more exotic sources like rotating white dwarfs. But ASKAP is particularly talented at finding Fast Radio Bursts, brief outbursts of radio waves coming from galaxies millions or even billions of light years away.

In a preprint paper released this month, a team at ASKAP reported a signal that looked like a startlingly bright Fast Radio Burst. It lasted the same general amount of time (only 30 billionths of a second) and emitted a broad range of radio frequencies. But unlike Fast Radio Bursts, it seemed to come from right outside the Earth's ionosphere.

When radio waves travel from faraway galaxies, they interact with electrons floating around in interstellar space. Those electrons slow down low-frequency waves more than the high-frequency waves, causing them to arrive at the telescope after the high-frequency ones. Astronomers call this effect "dispersion," and it works as a rough proxy for distance. Since we know about how many free electrons there are in every direction, we can calculate how far radio waves must have traveled through those electrons to be delayed a certain amount.

But for the recent ASKAP burst, there was barely any delay between the high- and low-frequency parts of the wave. The burst came from our own neighborhood.

Radio astronomers have a touchy history with things that look like Fast Radio Bursts but come from nearby. For a long time, mysterious signals called perytons showed up all over the place, until a group realized it was actually the microwave oven in the observatory break room.

Needless to say, microwaves are now kept under strict control at radio telescopes. So what was this new signal?

Tracking down an undead satellite

Reasoning that the only things floating around in nearby space that might release radio waves are satellites, the ASKAP team started searching. They compared the point of origin of the burst to maps of satellites. But the only matching satellite, Relay 2, hasn't been in operation since 1965.

Relay 2 was a NASA telecommunications satellite with a handful of physics experiments onboard, all long since defunct. According to NASA reports, it's been more than 50 years since anyone has purposefully used Relay 2.

While it's possible NASA is using Relay 2 secretly, the ASKAP team doesn't think this is likely. The plans for the satellite are publicly available, and nothing onboard is capable of producing such a short, bright burst.

The explanation

The team proposes two possible explanations for this strange emission. In the first, solar winds slam into Relay 2, building up charge against one plate of the satellite like rocks by the ocean build up salt. When the charge becomes so strong that the scant gas molecules between one plate and another can't take it anymore, the gas ionizes, releasing a sudden burst of visible light and radio waves. This is called electrostatic discharge. It's like lightning for satellites.

The other option is that micrometeoroids are slamming into the satellite, creating a cloud of dust and plasma right around the satellite. Then electrostatic discharge can happen even more easily.

It will be hard to tell which of these options is at play without observing Relay 2 over a long period of time. If the radio bursts happen at regular intervals, then they likely come from electrostatic discharge after a buildup. Micrometeoroids, on the other hand, wouldn't stick to a schedule.

Either way, observing short radio bursts from satellites may be a new way to probe the electric composition of space right outside the ionosphere.

Last February, a remote research station in the Canadian High Arctic captured a striking image of the night sky. It showed a dense network of bright streaks against the blackness. Those streaks were satellites, hundreds of them. 

Western University in Ontario and Defence Research and Development Canada collaborated to install 14 cameras at the tiny research station of Eureka on Ellesmere Island. Typically used to track meteors, these cameras monitor satellite activity over Canada. Each camera takes tens of images a second throughout the night. Together, the 14 cameras capture the full night sky. 

Taking so many photos so quickly allows them to track anything over 30cm wide passing overhead, including satellites. By combining all of the frames into one composite, the team created a long-exposure image that shows the trajectory of every satellite that passed over the region in one night. The result is both beautiful and startling. The trails of manmade objects in low orbit fill the sky like a woven fabric.

The launch of thousands of new satellites in recent years, especially mega-clusters such as Starlink, has transformed the sky by creating this visual clutter. The average person doesn't notice it, but it's become increasingly difficult for astronomers to observe the natural night sky. Satellite trails interfere with long-exposure images of stars and galaxies. It is vital that we can continue to observe the universe from Earth without peering through a haze of artificial lights.

Four similar stations exist elsewhere in Canada, in central British Columbia and in Saskatchewan. Over one year, the sites have collected nearly half a billion satellite observations, tracking more than 17,000 objects in orbit.

In Chile, a monumental telescope has opened its eyes. The telescope at Vera C. Rubin Observatory is the largest digital camera ever built, with a resolution of 3200 megapixels. It will photograph the entire southern sky every three nights.

Today, the team behind this ambitious project released the telescope's first images of the sky, which astronomers call "first light."

Over 10 years, the Vera C. Rubin Observatory (VRO) will create a time-lapse movie of the changing universe. Explosions from massive stars in other galaxies, pulsating stars, and asteroids make up most of the VRO's targets. Objects like these, called transients, change on timescales observable to humans. By contrast, most things in space look the same today as they would a thousand years from now.

Unprecedented scale

The VRO will acquire astronomical data at an unprecedented scale. It will rapidly outpace the combined data of every single other telescope in history, both on Earth and in orbit. As a consequence, it will blow open the door on transient astronomy. Before the VRO, astronomers discovered thousands of supernovae every year. With it, they will discover thousands every night.

But the VRO won't just focus on the distant universe. The camera also picks up nearby objects like asteroids and comets darting across the field of view. Today, we know of about one million of these rocky bodies in our solar system. The VRO will find five million more, dramatically improving our understanding of the danger Earth faces from medium-sized asteroids.

More than 40 international organizations contributed to the telescope, which sits on the 2,682m summit of Cerro Pachón in Chile. The telescope's main mirror, which is the size of a small car, journeyed to Chile from the Mirror Lab at the University of Arizona.

At the press conference announcing the first light images, Chilean ambassador Juan Gabriel Valdes discussed the key role Chile plays in astronomy.

"Astronomy is part of our identity and our heritage," he said, noting that protecting their dark skies is crucial for the world's space science. "Today, more than 40% of the world's astronomical observations take place in Chile."

The mother of dark matter

Vera C. Rubin -- the woman, not the observatory -- made a name for herself in the mid-20th century as a determined scientist in the face of entrenched sexism. Rubin found the first evidence for dark matter when she observed that galaxies rotate faster than their visible matter explains. There must be, she reasoned, additional invisible matter holding them together.

Nowadays, dark matter is a household term, even if no one (including astronomers) knows what it is. But Rubin, like many other female scientists responsible for key discoveries, never received the Nobel Prize.

Although the bread and butter of the VRO is transients, it can also probe how light bends around distant galaxies. The amount it bends depends on how massive galaxies are -- another clue to how much dark matter exists in the universe.

Harriet Kung, director of science at the Department of Energy, summarized the questions on dark matter and dark energy that the VRO will help answer.

"How can we better understand the matter and energy that make up 95% of our universe? Why is our universe expanding quickly, and how does that change over time? What role does dark matter play in how our universe evolved?"

First light

"The movie is starting," announced Kenneth Wright, director of development for the Office of Science and Technology Policy. "The camera is running. And we're gonna see our universe unfold before us."

The first image revealed in today's press conference showed two Milky Way-like spirals whirling against a background of more distant, yellower galaxies. This image comprises only 2% of the telescope's full field of view.

Since the camera can photograph light from the near-ultraviolet to the near-infrared, the colors in this photograph are more dramatic than what the naked eye would see. Galaxies that look blue emit strongly in the ultraviolet, while reddish-yellow galaxies shine in the infrared.

Red galaxies tend to be older, made up of aging stars that don't spit out the violet ultraviolet radiation of young blue ones. They also lose their defined spiral arms, as in the large elliptical galaxy in the first light image below. Many of the galaxies here comprise the Virgo Supercluster, a massive family of galaxies about 65 million light years away.

Moving asteroids

In a sneak peek of the VRO's time-lapse power, the observatory's director released a video of asteroids moving against the static background of stars. Every asteroid in this video, shown with a turquoise dot, was previously unknown. None of them are on an interception course with Earth.

In just one week, the VRO found 2,100 previously unknown asteroids.

Unparalleled resolution

The final first light image released shows the nearby Trifid and Lagoon Nebulae, yet another strength of this versatile telescope. Dark streaks against clouds of glowing dust and gas show regions of high density where baby stars are forming. Because the telescope was designed to see things very far away, turning it on such close objects allows it to zoom in with the resolution of 400 ultra-high definition TVs stacked next to each other.

A new view on the universe

Maryam Modjaz, a professor of astronomy at the University of Virginia and a member of the VRO science collaboration, explains that the VRO will transform how she does research.

"I’m particularly interested in very young supernovae, right after the explosion," she says.

Right now, astronomers have to be lucky to find these objects. More often, they don't catch them until days after they've exploded, missing crucial early information. That won't be an issue with the VRO, says Modjaz. "We can study the stars that gave rise to those explosions in what I call a 'stellar forensics' investigation."

The VRO is open to more than just astronomers. The observatory has just released its Skyviewer app, where anyone around the world can explore this project, which it calls the Legacy Survey of Space and Time.

In recent years, we have shown many spectacular images from the James Webb Space Telescope. The difference between them is that the JWST looks at very fine detail, while the Vera Rubin Observatory focuses on the big picture. After the VRO finds something new, the JWST can follow up for a more precise study.

Astronomers have filmed what seems to be the birth of a new planet within a swirling disk of dust and gas around a young star. On June 9, researchers photographed the cosmic event through the European Southern Observatory’s Very Large Telescope in Chile. 

The star, RIK 113, sits within the Scorpius constellation, 431 light years away. A large, rotating protoplanetary disk of dust and gas left over from the star’s formation surrounds it. In theory, the disk should eventually condense under the star's gravitational pressure to create a new planet. Some atmospheric emissions between the gas ring and the young star are also consistent with those that would be released from a planet in formation.

The images reveal complex structures within the disk, which extends out 130 astronomical units (19.5 billion kilometers) from the star it surrounds. Within this, there is also a bright ring that sits 50 astronomical units (7.5 billion kilometers) from its parent star. By comparison, Earth sits just one astronomical unit away from our sun. 

The images show spiral arms extending out from the inner ring, and this part of the image has most excited astronomers.

“One rarely finds a system with both rings and spiral arms in a configuration that almost perfectly fits the predictions of how a forming planet is supposed to shape its parent disk according to theoretical models,” said the research team.

If the presence of a planet is confirmed, this would be one of the clearest examples of planetary birth that astronomers have ever observed. To confirm their theory, the team has secured valuable observation time on the James Webb Space Telescope, which should give even sharper views of the region. 

It took millions of years of being a species before humans took the first picture of our own Earth's southernmost point. Now, after less than a century in space, we've photographed the Sun's south pole.

The European Space Agency's Solar Orbiter's images aren't just groundbreaking. Learning more about our star's polar regions will help scientists understand and predict the Sun's effects on Earth.

A new point of view

For all human history, we have had only one angle on the Sun. The view was straight on. This is because the planets and their spacecraft rotate around the Sun on a flat circle called the ecliptic plane. Picture a CD playing. Or don't, I'm not your boss. At any rate, that flat-on angle prevented us from seeing either pole.

Escaping the ecliptic plane takes some doing, by which I mean a lot of very expensive rocket fuel. The Solar Orbiter used Venus's gravity to help pull it out of the usual equatorial orbit around the Sun. Every time it passes Venus, the planet's massive gravitational force shoves it out of the ecliptic plane. As it keeps looping around Venus, it gets pushed further and further out of alignment with that plane.

In January 2027, it should come around the Sun again at a more tilted angle, giving us an even better view.

Weird magnetic fields at the sun's south pole

The Sun's polar regions are pretty busy and chaotic places, it turns out. The ESA's press release about their findings goes so far as to call the Sun’s magnetic field "a mess." The Sun's magnetic north and south poles switch places every 11 years, and it's a somewhat sloppy process.

During the transition period, called the "Solar Maximum," the magnetic field becomes a confused tangle, with no clear north or south pole. These magnetic upsets can cause a variety of startling and unpleasant effects on Earth, as seen in the history of solar superstorms. Look forward to power outages, satellite communication breakdowns, and particularly striking auroral displays until the sun settles down again and decides which end is which.

The images and readings from the Solar Orbiter give scientists a better idea of what's going on with the Sun's magnetic fields. This, in turn, will allow them to predict future solar activity more accurately. We aren't there yet, but this is a massive step toward building accurate computer models of solar magnetic behavior.

Specialists at Australia's Square Kilometer Array (SKA) released a report this week showing Starlink's unexpected impact on radio astronomy. Despite national and international protections against radio emissions in certain bands, Starlink is clogging the skies with electromagnetic pollution.

A crowded spectrum

Light pollution stretches far beyond the hazy glow of a city on the horizon. Down in the radio portion of the electromagnetic spectrum, governments barter sections of light. Large portions of bandwidth stay reserved for the military, while others get auctioned off (sometimes literally) to communications companies. Squeezed in between these chunks of spectrum lie bands for public broadcasting, HAM radio, and science.

Governments, corporations, and private citizens are supposed to stay away from protected bands so that radio telescopes can observe in peace. When the Starlink satellites launched, SpaceX collaborated with key radio astronomy observatories to avoid broadcasting while transiting above telescopes. Strategies include turning off Starlink WiFi services completely in certain regions of the sky.

The resulting disruptions to Starlink operations are not insignificant. Spectrum management, especially in the United States, involves give-and-take on both sides. But American observatories have the benefit of observing at mid- to high-frequencies, at least by radio standards. Those frequency bands are less polluted than low frequencies, because emitting at low frequencies takes less energy and so costs less.

'Unintended electromagnetic radiation'

If corporations and the military ignored protected bands, it would cause serious problems for radio astronomy. But a new study by engineers at the SKA suggests unintended electromagnetic radiation, or UEMR, may be a bigger issue than intended radiation.

The SKA is still under construction. When completed, it will be the most powerful radio telescope in the world. The low-frequency part of the telescope (SKA-Low) is designed to go after trace echoes from when matter began to coalesce 13 billion years ago. SKA-Low looks odd even by the standards of radio telescopes. A thick forest of metallic Christmas trees in the Australian desert maximizes sensitivity to faint signals.

But the new era of radio telescopes is butting up against a new era of satellites. There are more satellites in orbit than ever before, including massive networks of related satellites called constellations. With 7,000 satellites in Low Earth Orbit, Starlink is the biggest constellation.

As they transit above SKA-Low, Starlink satellites release radio emissions through multiple protected bands. In a pre-print of their study, the SKA-Low team reports 112,534 intrusions of Starlink satellites in their radio images. Their month-long study showed that 30% of all Starlink satellites in the sky at the time appear in their data.

Most of this emission seems to be accidental. UEMR from Starlink interfering with radio astronomy isn't unprecedented. During the initial launch phase, radio astronomers found that the propulsion system on the satellites emitted at unexpectedly low frequencies, decreasing the quality of astronomical data in an already polluted band. But the satellites had all been launched at the time of this new study. So where is all this radio pollution coming from?

No answers, and no regulation

We don't know the various origins of the UEMR the SKA-Low team observed, except for one feature at 99.7 MHz. If that sounds like an FM radio band, it's no coincidence. Starlink satellites bounce FM radio shows back down to the Earth. For telescopes carefully located in radio-quiet zones, that's not ideal.

Fixing this issue is particularly crucial to the success of SKA-Low, which seeks to look further back in time than any telescopes in a similar radio band. Signals from the early universe are very faint, and Starlink satellites are not.

Unfortunately, the codes governing spectrum use only ban intended radio emission in protected bands. Consider a hyperbolic analogy: Imagine if murder were illegal, but manslaughter wasn't. Spectrum experts and regulators are currently discussing how to address this issue. For now, though, as long as Starlink is here, so are the unintended radio emissions.

Last week, the Trump administration released a presidential budget request that would cancel almost all NASA science missions in order to focus on putting humans on Mars. It's mainly a showy, we-can-do-it project.

Mere weeks before, the CEO of a small San Francisco non-profit argued in a new paper that we need to start seriously considering terraforming Mars. The priorities of the two groups could not be more different.

The lead author of the paper, Erika DeBenedictis, received the prestigious Astera Fellowship to found Pioneer Labs, a small startup dedicated to designing microbes for terraforming. In The Case for Mars Terraforming Research, published last month in Nature Astronomy, she and her co-authors explain why terraforming studies are important. They also address how little we still know about potentially terraforming Mars. The main takeaway: Mars is not ready for humans, and humans are not ready for Mars.

Why bother with all this, anyway?

For some readers, the question of colonizing Mars isn't why, but how. If that's you, feel free to skip ahead. But others might approach the matter with more skepticism.

Space colonization has become a political byword, but opposition is far from new. Perhaps most famously (at least among us science geeks), Gil Scott-Heron's 1970 poem Whitey on the Moon contrasted the poverty conditions of many Black Americans with the perceived excess of the Apollo missions.

"I can't pay no doctor bill (but Whitey's on the Moon)," he wrote. "Ten years from now, I'll be paying still (while Whitey's on the Moon)."

From this vantage point, is spending billions on terraforming research anything more than a nationalist vanity project? DeBenedictis and her team argue that it is important.

"Technologies developed for Mars habitation, such as desiccation-resistant crops...will probably benefit Earth," they write.

In an older interview with the Astera Institute, DeBenedictis summed up this aspect of the paper's argument.

"Researching the possibility of a green Mars involves an infinite number of steps, all of which are in the right direction. How do we make human presence net-positive for the surrounding environment, rather than net-negative?"

Unlike the Trump administration, the study doesn't advocate for current human spaceflight to Mars. Instead, it proposes taking the questions of colonization seriously, starting from first principles. Should we? How would we? What would the future of Mars look like?

Not just science fiction

You'd be forgiven for assuming terraforming is just science fiction. But unlike faster-than-light travel, this staple of space adventure has a real scientific basis behind it.

The new study lays out a timeline for terraforming Mars, and it's a lot more rapid than you might expect. They propose that careful bioengineering can accelerate the formation of an ecosystem. Instead of the billions of years it took Earth to turn green, Mars could achieve it in a few decades.

The key to this rapid progression would be the development of microbes that thrive on Mars. Bypassing the labyrinth of evolution, humans could combine traits of Earth-based microbes such as temperature tolerance (surface temperature on Mars swings from -150°C to +20°C), invulnerability to fierce radiation and toxic gas, and no preference for atmospheric pressure. Such species could lead to an algae-covered Mars within decades.

How scientists would prevent such hardy microbes from disrupting ecosystems on Earth, the team doesn't address.

The natural advantages of Mars

According to their estimates, if all the water ice on Mars melted, it could form 10,000,000 km² of ocean at a depth of 300m. That's far less than the amount of liquid water on Earth, but it's enough to support long-term life on Mars.

In turn, the melting of Martian ice caps, which include both water and carbon dioxide ice, would increase atmospheric pressure. A thicker atmosphere would lessen the dramatic temperature swings between Martian night and day, in turn allowing the proliferation of life.

Martian soil also includes the necessary components for agriculture. Science fiction author Andy Weir exploited this so his marooned protagonist could grow potatoes in the hit 2017 science-fiction novel The Martian.

Such calculations have led planetary scientists to scour Mars for evidence of past life, mostly through remote sensing. (Soil samples are notoriously difficult to return to Earth for testing.) So far, they haven't found any evidence of life, only evidence of conditions necessary for life at some point in the distant past.

So, are we missing something?

The big unknowns

This is where DeBenedictis and Pioneer Labs' vision of Mars colonization research differs most dramatically from that of Elon Musk and SpaceX. The gist of the new paper is not that terraforming should happen now, but that scientists from different disciplines need to consider terraforming when designing future projects.

In planetary science, for example, the paper argues for continued research on everything we don't know about Mars. For instance, ice covers one-third of the planet. What's under it? More ice? Networks of caves? Liquid water? The answer could portend wildly different visions of a bioactive Mars.

They also call for extensive simulations of dust storms, a notable feature of Martian weather. Right now, planetary scientists understand dust storms on Mars fairly well. But how would dust change the atmosphere in a warmer, wetter Mars? How would the new climate alter the strength of the dust storms?

But perhaps the biggest open question for terraforming is whether Mars has enough electron acceptors to support life. Electron acceptors are molecules capable of transferring electrons -- and thereby energy -- down a chemical chain. They include carbon dioxide and nitrates, and are vital not only for photosynthesis, but also for human respiration.

Where to go from here

Despite their affiliation with Pioneer Labs, which focuses on microbe engineering, the authors don't call for the scientific community to jump on the terraforming bandwagon.

"While the possibilities are exciting, anything as big as modification of a planetary climate has major consequences and would require careful thought," they write. "But until we do more research, we do not even know what is physically or biologically possible."

In other words: research now, decide later.

"Priorities include quantifying H₂O, N_2, and CO₂ reserves...soil sample return, test missions for proof of concept of warming methods, and climate feedback studies," they explain, linking various NASA science directives with terraforming questions.

Current NASA goals for Mars already support human exploration, they add. "No abrupt change of course is needed."

But an abrupt change of course is in store for NASA. The presidential budget request cancels all Mars research missions except for the Martian Moons eXploration, which is mostly funded by the Japan Aerospace Exploration Agency. It still wants to put colonists on Mars, but without laying the scientific groundwork first. If science takes up Mars terraforming research, it will be without the United States.

A new dwarf planet named 2017 OF201 has been discovered far beyond Neptune. It sits in a region previously thought to be empty. Its existence raises questions about the structure of our solar system and the hypothetical Planet Nine -- a hidden, massive planet hiding somewhere out there in the outer reaches.

The dwarf planet's orbit is such an elongated ellipse that it takes around 25,000 years to make one orbit of our sun. At its closest, it sits approximately 6.66 billion kilometers away from the sun. At its furthest, it is a staggering 244 billion kilometers, about 54 times further away than Neptune. This giant orbit suggests that gravity from other massive bodies could be influencing it, possibly even a mysterious Planet Nine.

This theory suggests that a large, unseen planet, about 5 to 10 times the mass of the Earth, lurks in the distant regions of the solar system. Its advocates believe that it is large enough to influence the orbit of objects beyond Neptune. The problem is that the orbit of 2017 OF201 does not align with the gravitational patterns predicted by the Planet Nine hypothesis. It orbits in a different direction from one that would be influenced by Planet Nine. However, some researchers pointed out that the study of 2017 OF201 only considers one specific orbit of Planet Nine in its calculations.

The size of Pluto

Astronomers estimate that 2017 OF201 is about 700 kilometers in diameter, similar to Pluto, the former planet reassigned to dwarf planet status in 2006. Because of its elongated orbit, it is visible from Earth for only brief periods, making further observations challenging. 

Planet Nine aside, the existence of this dwarf planet challenges the idea that the outer solar system has few sizeable objects in it. It is now likely that many more distant objects are out there, still detected. This would reshape our understanding of the solar system's architecture. 

Back in the prehistoric days of theoretical astrophysics (1985), in a mystical and exotic corner of planet Earth (Fresno, California), a man sat in the back of a car and tried to break the spacetime continuum. His name was Kip Thorne: future scientific consultant on the movie Interstellar, future Nobel Prize winner, and all-around geek.

While he was a respected and innovative theoretical physicist, Thorne had not yet garnered a reputation as the mathematical mind behind some of science fiction's trickiest plot points. He was, instead, known for his deft familiarity with Einstein's equations of general relativity, a flexible set of conditions for how space and time interact. His friend Carl Sagan had called him up for help in solving a problem in his in-progress novel Contact, about radio astronomers who connect with interstellar beings.

Sagan, a science communicator by trade but an astrobiologist by training, needed Thorne's expert eye for the finer points of general relativity. He needed his heroine to get from the Earth to Vega, a journey of 26 light-years. And he needed her to get there fast.

Hyperspace

His initial treatment featured her plunging into a black hole, which carried her on a shortcut through hyperspace to Vega. Hyperspace isn't just a convenient term for hand-wavy science fiction authors. It's a real geometric concept describing space that occupies more than three dimensions. In short, Sagan's protagonist might travel through a fourth dimension, along a route where the distance from Earth to Vega is much less than 26 light-years.

Thorne wasn't having it. After all, all the matter and light that crossed the event horizon of the black hole would congregate at the singularity, accelerated to ultrarelativistic speeds.

"The calculations were unequivocal," Thorne wrote in Black Holes and Time Warps. "Any vehicle for hyperspace travel gets destroyed by the explosive 'rain' before the trip can be launched. Carl's novel had to be changed."

He proposed something even spacier than black holes: wormholes.

The temptation of wormholes

"If this FTL drive isn't fixed soon, we're dead!"

That's Captain Lee Adama on Battlestar Galactica, and as much as they reference it, the show never explained exactly how their faster-than-lightspeed (FTL) drive actually worked. They're not the only ones. Most science fiction properties lean on an implication of hyperspace tunnels, or wormholes.

In Hitchhiker's Guide to the Galaxy, most ships travel via hyperspace expressways. In Martha Wells' Murderbot series, the sardonic main character hitches rides through wormholes, although how these wormholes form or operate is left up to the imagination. Other authors, like CJ Cherryh, try to throw in a bit more of a theoretical physics vibe, with phrases like "Einstein-Rosen bridge." That's just a fancy name for a wormhole.

The truth is that although FTL travel is the backbone of science fiction, no one has figured out how it might actually work. Kip Thorne's proposition of wormholes, though, shaped the genre for decades.

The tempting thing about wormholes is that they are, in fact, a mathematically sound solution to Einstein's equations. It is absolutely possible for a tunnel to exist between two points in space such that the distance inside the tunnel is shorter than outside. What's not so clear is how such an object could form, or how it could stay open if it did.

The problem with wormholes, Part I

What Thorne struggled with in the backseat of a car in 1985, trying to fix Carl Sagan's plot, is that wormholes don't want to be used for interstellar travel. Previous physicists found that they have a fatal flaw. All the matter that passes through a wormhole causes it to gravitationally contract. Right after forming, it closes. Nothing gets all the way through.

This is called pinching, and Thorne needed to avoid it for Carl Sagan's sake. He calculated that the only way around pinching is to coat the inside of the wormhole with "exotic matter." Exotic matter has a negative energy density from the perspective of light passing through the wormhole.

When traveling at light speed, Einstein's equations result in strange effects, and one of those is that negative energy density isn't technically forbidden.

Thorne's conjectures inspired a flurry of papers on exotic matter and whether it could coat a wormhole. The results, to this day, are inconclusive. We do know that exotic matter actually exists, at least near black holes, where the event horizon disrupts energy fluctuations in a way that favors negative energy density. The same occurs when two uncharged plates approach one another. But we don't know whether such matter would stay exotic on the inside of a wormhole.

For Contact, Thorne was content to skip over the finer details of how the Vega aliens coat their wormhole with exotic matter. But academically, he and his collaborators were only getting started.

The problem with wormholes, Part II

Say we have exotic matter. Say we can use it to coat the insides of a wormhole so that the sides repel each other and stay open. How do we go about finding a wormhole?

As bizarre as black holes seem, they have a perfectly reasonable origin story. When massive stars get very heavy and can no longer hold themselves up against their own gravity, they collapse into an infinitesimally small point. That's a black hole.

But there's no similar mechanism for the formation of wormholes. At least, not for those large enough to allow travel. At the quantum level, Kip Thorne's graduate advisor, John Wheeler, laid the groundwork for wormhole formation back in the 1960s. He predicted that at very, very small scales, all spacetime should froth and bubble. Based on a fundamental theorem of quantum physics called the Heisenberg Uncertainty Principle, this "quantum foam" might form very small wormholes every second and annihilate them the next.

So can one forcibly enlarge a wormhole from the quantum to the classical regime? The answer lies in the realm of quantum gravity -- an enduring and unobtained Holy Grail in theoretical physics.

That's a no-go.

How wormholes imply time travel

Let us create a wormhole through unspecified quantum mechanical processes. Despite its immaculate conception, free of the bizarre time effects plaguing other proposed creation mechanisms, it will still succumb to the temptation of time travel.

The classic example, first conceptualized by Kip Thorne shortly after his contact with Contact, banks on an effect called time dilation. When objects move very close to the speed of light, the time that the object experiences flows more slowly than the time of a stationary observer. Think of Ender's Game, in which the protagonist skips forward 2000 years between the first two books because of how much time he's spent on very fast spaceships.

If Ender takes one end of a wormhole with him on his spaceship and leaves the other end on Earth with his sister Valentine, the wormhole will connect his sister to his time frame. Say he spends 10 months on a round-trip voyage and winds up back on Earth where he started. Then 10 months after his departure, Valentine can look through the wormhole and see him back on Earth.

But say that thanks to time dilation, from Valentine's perspective on Earth, Ender's trip takes 10 years. When he finally returns to Earth, entering his side of the wormhole will return her to her side, 9 years and 2 months before.

More paradoxes

This is where all sorts of paradoxes come into play. What if, for instance, Ender uses this setup to journey 50 years into the past and kill his own grandfather? The world misses out on one very enjoyable novel and quite a number of mediocre ones (sorry, Speaker for the Dead fans). Then no Ender would exist to go kill his grandfather, so his grandfather would live, and Ender would be born once more.

Bizarrely, that scenario actually makes perfect sense in a quantum mechanical world. The laws of quantum mechanics don't predict outcomes, just the probability of different outcomes. Attempting to understand what that actually means is an entire branch of physics called quantum foundations. It leads to elegant but unsettling theories such as Hugh Everett's "many-worlds" theory of splitting timelines. Each time a quantum mechanical system is tested, Everett proposes, the universe settles into one of many possible timelines, branching constantly.

This fits in nicely with the grandfather paradox. There is some probability that a man arrives out of nowhere and murders Grandfather Wiggin in his youth. There exists some other probability that Grandfather Wiggin carries on happily, eventually allowing Ender to be born and travel backward in time. When the moment comes for him to die, the universe makes a choice. We lift the lid and peer in on Schrodinger's grandfather: either he's alive or dead, but a second ago, he was both.

Why time travel (probably) can't exist

So, as far as we can tell, under the basic principles of quantum mechanics, time travel isn't as obviously a no-go as one might assume.

Yet we know of at least one mechanism by which any wormhole acting as a time machine might destroy itself. Kip Thorne, his graduate student Sung-Won Kim, and Stephen Hawking calculated that the same kind of quantum foam present in all space might build up inside a wormhole, destroying everything inside it and causing it to pinch shut.

The keyword here is might. We don't know enough about quantum gravity to say whether it would.

Hawking hypothesized that the universe would protect itself from time travel to avoid the manifestation of quantum phenomena on a human scale. More importantly, he wrote, this would "make the universe safe for historians."

He tested his theory in 2008 by hosting a party for time travelers. The day after the party, he sent out the invitations. No one showed up.

A majority of physicists agree with his conjecture. But to this day, no one can conclusively resolve it. That would require a working theory of quantum gravity. We're a long way away from that -- unless anyone from the future wants to help us out.

How do you speed up something that only interacts regularly with itself?

That's the question gripping astrophysicists at the Cubic Kilometer Neutrino Telescope (KM3NeT). In 2023, before the telescope was even completed, a high-energy neutrino shot through the Earth's atmosphere and into the detection zone of KM3NeT. Since KM3NeT looks for neutrinos, finding one wasn't a huge surprise. But this was the most energetic neutrino ever detected. So energetic, in fact, that it crashed their computer.

Where did it come from?

A telescope at the bottom of the ocean

KM3NeT looks about as much like a traditional telescope as, say, a rhinoceros does. It consists of indented spheres of metal standing guard over smaller glass spheres hanging from strings. The whole contraption sits 3,500m underwater at the bottom of the Mediterranean Sea.

Its strange design comes from its purpose: to hunt some of the most elusive particles in the universe. Neutrinos are omnipresent, with over a billion of them flowing through each square centimeter of space every second. But they barely interact with matter, and not at all with light or magnetic fields.

Still, some dramatic events create ultrarelativistic neutrinos that move at almost the speed of light. Both cosmic rays hitting the upper atmosphere and supernovae create neutrinos observable from Earth. Astrophysicists try to detect these energetic neutrinos.

But detecting something that doesn't interact with light, magnetism, or most matter is mildly challenging, to say the least. The most famous neutrino detector in the world, IceCube, uses the Antarctic ice sheet to do so. KM3NeT opts for the salty waters of the Mediterranean Sea.

In water, light travels at only 75% of its speed in air, but neutrinos keep speeding along at the same velocity they always have. But even for a weakly interacting particle, 3,500m of water is a lot of water. Very occasionally, neutrinos collide with a proton or electron in the water with exactly the right angle and momentum to interact via the weak nuclear force.

These interactions can produce charged particles, including muons, which are more susceptible to interactions with matter. When the muons hit water molecules at velocities higher than the speed of light in water, they create a shock wave akin to a sonic boom. That, in turn, releases blue light called Cherenkov radiation.

The suspended spheres of glass and metal in KM3NeT are optical detectors searching for this Cherenkov glow. When they detect it, they use its strength and direction to trace back where the muon-molecule collision happened and what the muon's energy was. From there, they can work out the energy of its parent neutrino.

The neutrino that crashed the computer

Lowering precious optical devices to the sea floor takes a lot of time. By February 13, 2023, only 6% of KM3NeT detectors were in place. They had been detecting a few neutrinos here and there, but that day, something strange came in.

"When I first tried looking at this event, my program crashed,” KM3NeT physicist Paschal Coyle told New Scientist.

It was a neutrino unlike anything seen before. Hundreds of times more energetic than the previous record-holder, it defied traditional astrophysical origins like supernovae, gamma ray bursts, or black hole accretion.

When they looked in the region of the sky from which the neutrino came, they found nothing. No signs of supernovae, energetic distant galaxies, or stellar collisions. Just empty space.

Empty space does have its own background field of neutrinos, but high-energy neutrinos are exceedingly rare.

The team's paper on the event came out earlier this year in Nature. In it, they calculate the rate at which we should be observing such neutrinos and find that about one should show up every 70 years. The chances that such a neutrino would show up one year into the run of a telescope that was only 6% completed are stunningly low.

The KM3NeT team has another hypothesis. Particle physicists have long theorized that high-energy cosmic rays (protons and electrons traveling near the speed of light) could interact with the background light of the universe and produce massively energetic neutrinos. This event would be exceedingly rare and has never previously been observed.

At least, as far as we know. It's possible that KM3NeT observed it in 2023. But astrophysicists have a lot of work to do before the identity of the mysterious neutrino is anywhere close to resolved.

For three and a half days earlier this month, Eric Philips, 62, was in an environment that made his familiar Antarctic plateau seem almost hospitable. Sardined in a tiny capsule with three other amateur astronauts, he orbited our blue marble at 7.6km/sec. Outside, the blackness of space, with its microgravity and zero air and unseen perils of radiation and micrometeorites.

"What never gets old is Zero G," Philips told ExplorersWeb. "It's like being a child all over again."

Previously, we explained how Philips' late-career adventure came about. Two years ago, he guided a ski tour on the Norwegian Arctic Islands of Svalbard. One of his clients, Chinese-born Maltese citizen Chun Wang, was interested in talking about space travel. Not uncommon: Simple environments often appeal to polar types.

But in this case, Chun had the resources to do more than talk. He had made a fortune in bitcoin mining and wanted to buy a commercial flight on SpaceX. A few months later, he invited Philips, Rabea Rogge (a German robotics engineer and fellow skier on the tour), and cinematographer Jannicke Mikkelsen, based in Longyearbyen on Svalbard, to join him. Chun would cover expenses, in the range of $200 million.

A year of training

For a year, Philips and his three partners trained for the mission, which they dubbed Fram2 after the famous Norwegian polar ship. Most of the training took place at SpaceX's headquarters in Los Angeles. The Dragon capsule flew on its own, but they had to learn what to do in case something went wrong. Among the things Philips had to practice as the designated medical officer was inserting a catheter in case of an emergency. However, all went well.

"In the end, we used maybe one percent of our training," said Philips.

On March 31, after several days in quarantine near Cape Canaveral in Florida to avoid catching a bug before the flight, it was time to launch.

Centrifuge training had given some practice with the tremendous G-forces of a rocket tearing itself free of Earth's gravity, but even that didn't compare to the 4.6 Gs of the real thing. It was enough for them to feel their organs compress, said Philips. But it didn't last long.

Kármán line

They cleared what is called the Kármán line, 100km above the Earth, at which point they were officially astronauts. Soon, the main engine expended its propellant and fell away. Almost immediately, the second engine kicked in, propelling them to an altitude of 200km. From there, onboard thrusters lifted the capsule into orbit, some 450km above the Earth.

The first sign of microgravity Philips noticed was the loose ends of his restraint straps beginning to float. At the same time, a mascot that astronauts call the Zero G Indicator began to float around the 2.5-meter-wide capsule. For this mission, their Zero G Indicator was a stuffed polar bear wearing an emperor penguin necklace.

This wasn't just a nod to Philips' background or where they met. This was the first time a spacecraft was planned to orbit the Earth via the Poles. From the 1957 launch of Sputnik until now, they have all been, from our perspective, "horizontal" orbits, not vertical.

"Because of our polar orbit, the Earth rotated beneath us, so we passed over every part of it," Philips told ExplorersWeb. "We're told this is a blue planet, because of all the oceans. But we were often over whiteness."

Pure silence

In orbit, Philips noticed how quiet it was. Freed from gravity and without the friction of the atmosphere to slow them, they flew (or rather, fell) around the Earth with only occasional need for the booster to kick in, to keep their orbit from deteriorating. When it fired, sparks appeared outside the window, like a little fireworks show.

SpaceX broadcast the launch on its website, and a program called Zero Six Zero showed the Earth in more or less real time, with a simulated version of the capsule moving above it. In almost no time, they made their first pass over the South Pole. Forty-five minutes later, they flew over the North Pole. Orbiting at 27,000kph, it took them just three-quarters of an hour to travel halfway around the world.

Every day, they went through multiple phases of darkness and light. They made 55 orbits in all. Always, Philips delighted in "the sheer joy of microgravity."

"What surprised me is how quickly I adapted," said Philips. "I'm sensitive to motion sickness, and I was likely to get terribly space sick. But the first day was great. On the second day, we all experienced a little nausea but quickly recovered."

A warm capsule

The interior temperature of the capsule ranged from 24˚ to 28˚C -- warm for polar travelers. When they needed to sleep, they climbed into thin sleeping bags and just floated around above their seats, bumping lightly into one another as they slept.

During the day, drifting around in the cramped space, they were often "a tangle of limbs," said Philips. His experience of being stuck in a small tent in Antarctic blizzards for three or four days at a time came in handy here.

Besides the otherworldly sensation of microgravity, everyone's favorite experience was their time in the Plexiglas cupola — a clear dome atop the capsule, just big enough for one person at a time. From there, they could take turns looking at both the blackness of space and our amazing planet below. The Plexiglas was solid enough to repel radiation and any micrometeorites that might strike it. During launch and splashdown, a protective nosecone covers the cupola.

Philips knew from his prior reading that, contrary to the old myth, the Great Wall of China is not visible from space -- and sure enough, it isn't. But he did notice at night how bright China was with artificial lights, "far more than any other country."

What he saw

He also identified other areas, both natural and manmade: their launch site at Cape Canaveral, the mountains of Alaska, and Svalbard, the archipelago that brought them all together. Philips also made out parts of Queen Maud Land in Antarctica, although at this time of year, darkness or twilight had settled over much of the White Continent.

The crew had 11 large satchels tucked away in a cargo section, containing food and water for five days. "It was like packing a sled," recalled Philips. The Australian was even able to enjoy coffee in space, although it probably didn't measure up to the typically excellent coffee in his own country.

For unclear reasons, SpaceX has always been shy about its onboard toilet facilities, and Philips and the others had to sign an NDA not to discuss it. Some space aficionados have pieced together information about it, however. Philips admitted that on such a short-duration flight, astronauts are administered enemas before launch to simplify the first couple of days.

700 astronauts

Since Yuri Gagarin, there have been almost 700 astronauts, but counting these four, there have only been 11 tourists who have gone beyond suborbital experiences and into outer space. As part of their program, they performed some 22 experiments, including taking the first X-ray in space and growing mushrooms. Cinematographer Jannicke Mikkelsen filmed. But largely, it was about soaking up an out-of-the-world experience.

When it came time to descend, they packed everything away -- including the Zero G Indicator -- put on their suits and strapped themselves in. "It was like being in a sailboat and preparing for an impending storm," said Philips. "You do your best to prevent items from flying around."

Their reentry also generated 4.6 Gs, but their brief time in weightlessness made it feel even more forceful than during the launch. Meanwhile, the temperature outside the capsule rose to 2,000˚C from friction in the atmosphere.

Two drogue parachutes deployed at about 5,500m in altitude while Dragon was moving at approximately 560kph. At about 1,800m, the drogues pulled out the four main parachutes. The Dragon hit the water at about 25kph off Oceanside, California -- the Dragon's first Pacific splashdown.

A ship waiting five kilometers away then came and winched the capsule on board. All the astronauts were able to exit the hatch by themselves, although one was a little shaky walking to the medical bay.

'A hurricane raged in my mind'

But after such an intense, at times ecstatic experience -- microgravity, seeing our planet for the first time from space -- there was bound to be a hangover. Philips recalled:

At the medical bay, my body went into shutdown. It was difficult to communicate with people in any meaningful way. A hurricane was raging in my mind. I could answer questions like, 'Are you in pain?' with no problem, but for two or three days, I couldn't describe the experience.

Days later, they still experienced floating sensations. Once at breakfast, Philips imagined he could float over to the buffet to get his food.

While their extraterrestrial experience made some past astronauts a little "spacey" in their afterlife on Earth, Philips isn't concerned.

"I'll remain the staunch skeptic I've always been," he says.

The year is 2021. On Earth, COVID-19 rages. NASA is finally about to launch the James Webb Space Telescope (JWST), prophesied to usher in a new era of astrophysics. And a Cambridge professor named Nikku Madhusudhan writes the unobtrusive first entry in his to-be trilogy of papers on nearby exoplanet K2-18b.

Madhusudhan and his two collaborators propose a new category of planet, which they dub a "Hycean" world. Much larger than Earth but smaller than Neptune, Hycean worlds would boast water oceans under a hydrogen-rich atmosphere. In terms of habitability, they would be more flexible than rocky worlds like Earth. Their atmospheres would keep their temperatures stable. They might even have plentiful aquatic life.

Flash forward to 2025, and astronomers have yet to confirm the existence of Hycean planets. But last week, Madhusudhan's team at Cambridge claimed the discovery of potential biosignatures on K2-18b, one of their candidate Hycean worlds. The biosignature in question is the molecule dimethyl sulfide, largely produced on Earth by phytoplankton.

Headlines around the world have run rampant with this sign that we might not be alone. However, what many outlets leave out is the history of the claims in question and the concerns raised by a host of astronomers, many of whom are deeply enthusiastic about the search for extraterrestrial life. The first "hints" of possible life, reported by the Cambridge team in 2023, met with widespread derision among the astronomical community. The same is true for this new evidence in 2025.

That's not to say that the new results are obviously false, or even that aliens are definitively not involved. But the story of dimethyl sulfide on K2-18b isn't a simple one.

JWST is the best in the game, but the game is a hard one

Sitting at 1.5 million kilometers from Earth, JWST is the premier instrument in the solar system for observing exoplanetary atmospheres.

Under irradiation from their host star, atoms and molecules tense up, absorbing light at specific wavelengths. When they relax again, they emit that light. Observing patterns of missing or surplus light allows astronomers to identify the chemistry of the universe.

Much of the field of astrochemistry focuses on either the diffuse gas in interstellar space or the dusty rings around protostars. While not simple, these systems don't hold a candle to the complexity of exoplanet atmospheres. Planets have so much gas, such turbulent atmospheres, and are so irradiated by their host star that their light signatures are a blurry mess. Different atoms and molecules all jockey with one another for space. If astrochemists typically deal with barcodes, exoplanet atmospheres are like identifiers from the 17th century, stored in a damp warehouse, half-eaten by moths.

Oh, and if you want to take a photo of it, you have to do it while it's on the hood of a car with its brights on. The light from stars overwhelms anything from the planet. Astronomers use JWST to analyze the light coming from the star while the planet is in front of it, and compare that to the light coming from the star while the planet is behind it. This technique, called transit spectroscopy, separates the light from the star and the light from the planet. It's also very, very difficult.

'Possible' biological activity

In October of 2023, Nikku Madhusudhan and his team published the results of their JWST observations of K2-18b. Their paper, entitled Carbon-bearing Molecules in a Possible Hycean Atmosphere, drew less attention for its carbon-bearing molecules and more for its discussion of dimethyl sulfide.

Unlike many other kinds of spectra, astronomers can only parse exoplanet spectra using complex models. These models run through different options -- more methane, less methane, more ammonia, less ammonia but at a higher temperature, etc. -- to find the best fit. But the models require educated guesses on what molecules might be in the atmosphere. The chosen molecules can greatly affect the model's conclusions.

So when the Cambridge team ran their models on their JWST spectra of K2-18b, they limited the options to typical molecules found in exoplanet atmospheres: water, methane, carbon dioxide, and so on. And then, building off their 2021 work on Hycean worlds, they added five molecules they identified as biosignatures. These included dimethyl sulfide.

The best-fit model incorporated dimethyl sulfide at low confidence. According to their model, there was a 66% chance they had detected dimethyl sulfide, and a 33% chance it was random noise. Further muddying the issue was the fact that the JWST instrument used has a gap in the region where dimethyl sulfide is strongest.

The authors theorized that the dimethyl sulfide might originate from an ocean filled with algae-like life, despite the lack of other chemical byproducts associated with phytoplankton. They admitted, however, that future observations were required.

Follow-up observations on dimethyl sulfide

“This is a revolutionary moment,” Nikku Madhusudhan told The New York Times in an article published last Thursday. His new results were soon to be published in The Astrophysical Journal Letters. A deluge of comments on the NYT piece asked to read the actual paper, to no avail until the following day, when the press embargo lifted before the actual paper came out. “It’s the first time humanity has seen potential biosignatures on a habitable planet,” the author enthused.

The Cambridge team's new paper reports on follow-up observations using a different instrument on JWST, this time without a gap in the region of interest. Their models came back with higher confidence this time. They also returned a hit for dimethyl disulfide, a relative of dimethyl sulfide and another potential biosignature.

Many astronomers noted the results were tentative, including Madhusudhan himself. "It is in no one’s interest to claim prematurely that we have detected life," he told The New York Times. But that didn't temper his enthusiasm. “Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have."

The pushback

Not everyone is as thrilled as Madusudhan.

ExplorersWeb spoke with Anthony Remijan, an astrochemist and interim director of Green Bank Observatory.

"There are probably dozens of molecules that can fit the extremely low resolution, low sensitivity of the 'features' seen in the JWST spectrum," said Remijan. "To claim they can be attributed to a singular, unique molecule such as DMS [dimethyl sulfide] is an extraordinary claim. As such, it should be reinforced by extraordinary data, which is not what we have here."

In fact, the new paper doesn't address a recent reanalysis of the 2023 data by a separate team that didn't find any evidence of DMS or even that K2-18b actually has an ocean. Some work has suggested K2-18b might be covered in magma rather than water, and therefore not a prime candidate for phytoplankton. Perhaps most crushingly, several recent papers show that dimethyl sulfide doesn't even need life to exist. It's also found on comets, which are not notable hotbeds of algae.

Remijan is particularly concerned about the validity of dimethyl sulfide as a biomarker.

"Over the past decade, interstellar urea was confirmed in the [interstellar medium] where at one point, urea was thought only to be formed by biological processes," he pointed out. Urea is the main component of urine. "Obviously, this is not the case in the [interstellar medium]."

'Practitioner vs commentator'

The Cambridge team acknowledges the uncertainties, but stand by their conclusions. When an interviewer brought up the biosignature issue on BBC Radio 4, Madhusudhan said, "This is the difference between a practitioner and a commentator. From a practitioner's point of view, this is as good as it gets in science, and you just have to recognize it. But for that, you have to be in the field, not outside."

As it happened, the interviewer questioning him was Chris Lintott, a published exoplanet astronomer.

In the press, too, some skeptical voices have tempered the hope for aliens. A scathing article in The Atlantic noted that "the word possible is doing load-bearing — if not Atlas-like work -- in these headlines."

Scientific American, meanwhile, interviewed Chris Lintott before his conversation with Madhusudhan on BBC Radio 4. "Dimethyl sulfide should exist in a chemical network," he told them. "If it’s produced by biology, it should break down, and the raw materials such as H₂S [hydrogen sulfide] used to make it should be visible in the spectrum, too. They aren’t."

A blind search for life

The day after the Cambridge team's press release, Nikku Madhusudhan's former graduate advisor, MIT astrophysicist Sara Seager, published a paper of her own. Along with her collaborators, she analyzed the sensitivity and precision of JWST's instruments in relation to exoplanet atmospheres. What she found wasn't hopeful.

In a world racked by insecurity, political strife, and environmental degradation, it's no surprise that so many of us want to believe in life on another planet. But according to Seager, we'll have to wait.

She writes, "With JWST, we may never be able to definitively claim the discovery of a biosignature gas in an exoplanet atmosphere."

And Anthony Remijan adds:

"To invoke a biological origin suggests there is no abiologic way to form these molecules, which is simply not the case. We are just beginning to scratch the surface on how molecules can form in these extreme environments, where [it was] once believed that no molecule should ever exist in space, except for hydrogen. So even if DMS was found in space, there is likely an abiogenic process we haven't thought of yet that formed it."

Everything that falls into a black hole falls in at the same time. Perhaps in the distant past, some unfortunate alien astronaut was sent past the event horizon to explore what lies beyond. From our perspective, he is still falling across the threshold. He has been since he first fell in, back before his civilization crumbled, before his home planet tumbled into its sun, and that sun collapsed into a white dwarf.

From his perspective, he only just crossed it. What will he find on the other side? As of right now, physics only has guesses. In this week's Great Mystery of Outer Space, we cover the uncertain insides of black holes.

Black holes might be mysterious, but they're real

Albert Einstein believed black holes to be a grand mistake. They were a natural extension of his theory of general relativity, a set of otherwise airtight formulations of how gravity and light behave, but they could not possibly be real. After all, how could anything have mass if it was infinitely small? How could it trap light within it, thereby removing information from the universe?

He set out to disprove their existence in a 1939 paper, and while his conclusions were correct, he started from a set of assumptions that were not.

Unfortunately for Einstein, the existence of black holes has now been proven over and over again. First, by strange X-rays from a star being shredded apart by something massive. Then came the ultra-bright radio emission in the center of galaxies from disks of matter orbiting an invisible center. Strange orbits, things lurking at the heart of supernovae remnants, and huge jets of plasma in distant galaxies all added evidence.

In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves from a pair of distant black holes colliding. And finally, in 2019, the Event Horizon Telescope (EHT) succeeded in directly imaging the center of nearby galaxy M87. Black holes don't emit light, and the shadow they leave is visible against the bright plasma around them. The EHT images of M87's black hole shadow are the closest we can get to photos of a black hole itself.

The anatomy of a black hole

Hear me out: black holes are the simplest objects in the universe. No, really, I promise. They only have two features of note.

The first is the event horizon, which isn't technically part of the black hole itself. Instead, it's the distance from the black hole where gravity becomes so strong that nothing, not even light, can escape the inexorable pull toward the center. Material caught in the black hole's orbit circles around the event horizon, disrupted by the strong gravity and by colliding with other matter. This is what causes the bright rings known as accretion disks and the flares called, in various different circumstances, quasars or active galactic nuclei.

Right at the event horizon is where things get very, very strange, but it's a known kind of strange. The laws of general relativity predict that everything that crosses the event horizon crosses it at the same time, and to an outside observer, things crossing it freeze. In fact, before physicist John Wheeler coined the term "black holes," most physicists referred to them as "frozen stars." (Personally, I find the original name much more evocative.)

Far below, at the center, lurks the singularity. It is an infinitely small point or, in certain peculiar cases, an infinitely thin ring. It can weigh up to 10¹¹ times the mass of the Sun. It has no dimensions, no volume, no time. But it has a lot of mass.

Just what is a singularity?

In the clumsiest terms, a singularity is a place that's very weird compared to everything else around it. The usual laws don't seem to behave so well around singularities; that's what makes them so singular. The idea of a point with infinite density makes sense on paper. It falls right out of Einstein's equations, much to the consternation of Einstein himself. But elsewhere in physics, the presence of singularities tends to indicate the theoretical models are missing a few components.

That's what many physicists believe is happening with the black hole singularity. The infinitely small point might not physically exist, but general relativity can't quite grapple with the true nature of black holes.

If the singularity is quite small but not infinitely so, then it's the purview of the theory known as quantum gravity. Unfortunately, quantum gravity barely exists.

The world of physics needs a mathematical formulation of how gravity behaves at small scales. It needs something revelatory and revolutionary, the quantum gravity equivalent of general relativity. That's a hard ask. The only widely popular framework to attempt it is string theory, an astoundingly beautiful theory of nature that, after more than 60 years of development, has yet to predict anything testable.

So the nature of the singularity remains, for now, a mystery.

Okay, but what would the 'singularity' actually do?

We don't know what a singularity is. Do we know what it does?

The answer is maybe. General relativity is a set of laws, not a recipe. Mathematically, there are many recipes for how space works that obey the laws of general relativity. Among these recipes (obscurely called "metrics" in physics lingo), several are more pertinent to our lived reality than the others.

The Schwarzschild metric, for instance, describes spacetime around spherically symmetric points, black holes included, as long as those points aren't spinning. The Kerr metric takes it a step further and describes spacetime around points that are spinning, which adds in a slew of bizarre effects with intimidating names like "frame dragging."

Buried in some of these distinct metrics are places where Einstein's equations give out. With well-understood metrics there as guide rails, physicists can fill in some of the blanks.

Currently, common thought is that the unknowable singularity at the center of a black hole probably devolves into three marginally more knowable ones as the black hole ages.

Singularities to watch out for

Three singularities in particular might haunt the insides of an aging black hole. We'll start with the worst news first: the BKL singularity. Formally named the Belinski–Khalatnikov–Lifshitz singularity after its discoverers, the BKL singularity is also known as the chaotic or oscillatory singularity. That's because as an observer approaches it, their body is subject to increasingly violent tidal forces that alternately stretch and compress them. If anything in a black hole is most out to get humans, it's the BKL singularity.

Then there's the ingoing singularity. All of the matter and light that falls into the black hole gathers together, falling for infinity. The gravity of this region can be so strong that it forms its own singularity. Good news, though: the region where matter congregates might be so thin that other objects can actually pass through it undeterred.

Similarly, the outgoing singularity arises from the light that bounces off things inside the event horizon and then travels backward, colliding with the ingoing singularity. What happens then is unclear, but once again, it might be avoidable.

The predictions above have serious mathematical credentials, but at the end of the day, the nature of the singularities are still unknown. So, too, is the state of matter inside a black hole. Can matter survive the event horizon? Where is it located? Is it converted to light or even gravitational waves?

We can only hope that a new theory of quantum gravity will illuminate the insides of a black hole.

High school student Matteo Paz has stunned the scientific community by identifying 1.5 million previously unknown objects in space. 

By creating an artificial intelligence algorithm, Paz found a way to sift through vast amounts of space data and uncover millions of cosmic objects hiding in plain sight. His work didn’t just impress scientists; it earned him the top prize at the 2025 Regeneron Science Talent Search — a $250,000 award that goes to the most promising young scientists in the U.S.

It all started during Caltech’s Planet Finder Academy in 2022. The summer outreach program is designed to give high schoolers hands-on experience in astronomy, and Paz was hooked. The following year, he signed up for a six-week Caltech program that pairs students with campus mentors. Paz was assigned to Davy Kirkpatrick.

"The first day I talked to him, I said that I was considering working on a paper to come out of this, which is a much larger goal than six weeks," said Paz. "He didn't discourage me. He said, ‘OK, so let's talk about that.' He has allowed an unbridled learning experience. I think that's why I've grown so much as a scientist.”

How do you make sense of so much information?

With encouragement from Kirkpatrick, Paz tasked himself with a daunting challenge: How do you process and make sense of nearly 200 terabytes of space data gathered by NASA’s NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer) telescope?

NEOWISE has been scanning the sky for asteroids for over a decade. At the same time, it has captured data on other variable objects. According to Caltech, these are “hard-to-catch phenomena like quasars, exploding stars, and paired stars eclipsing each other.” The NASA telescope was able to detect the varying heat of these objects, but the sheer size of the dataset made it impossible for human astronomers to comb through them.

With almost 200 billion rows of data, going through it by hand was never an option, and Paz never considered it. The 18-year-old had a knack for AI, coding, and computer science. Combining this with his substantial math knowledge (he has been studying advanced undergraduate math for the last few years), he created an AI model to sift through the data for him. 

Machine learning

In the short six-week program, he began using machine learning to make an AI model that could recognize patterns in the infrared data — subtle signals that might indicate the presence of cosmic objects. Kirkpatrick acted as an astronomy consultant and helped him interpret the data. 

The duo kept working on the project after the six weeks were up. By 2024, Paz was mentoring other high school students on the subject. Now the model can tear through the raw data from the NEOWISE telescope. They have made a jaw-dropping 1.5 million discoveries, each a potential new clue about the structure and history of our universe.

Since winning the 2025 Regeneron Science Talent Search, Paz hasn’t slowed down. He and Kirkpatrick hope to publish the complete catalog of newly found objects this year. Paz has also secured his first paid job. He is working at Caltech, continuing his research and collaborating with astrophysicists on how to scale his AI system for even bigger projects. 

Imagine drifting alone in space, with no cord connecting you to anything. It’s the stuff of nightmares or the freedom of dreams, depending on how you look at it.

In 1984, four astronauts did just that, and footage from their untethered flights is again making the rounds, reminding everybody of how incredible -- and frightening -- the emptiness of space can be. 

NASA astronaut Bruce McCandless II stepped away from the Space Shuttle Challenger on Feb. 7, 1984, using a jet-powered backpack called the Manned Manoeuvring Unit (MMU). He was the first human to float untethered in space. The image of him drifting alone above the Earth is considered the most terrifying space photo ever taken.

His spacewalk was not a stunt. It was the first demonstration of a cutting-edge tool designed to help satellite repair and space station construction. Drifting 90 meters away from the shuttle, he showed that astronauts could operate freely in space. Until then, the idea had been purely theoretical.

Two days later, fellow astronaut Bob Stewart also donned an MMU, and both men leaped from the shuttle into space.

A complicated mission

Just months later, NASA would put the MMU to an even greater test. During a November 1984 mission, astronauts Dale Gardner and Joseph Allen donned MMUs for a space salvage mission. Two communications satellites had failed to reach their intended orbit. Rather than letting them become space junk, NASA decided to try and retrieve them.

Once their space shuttle was within nine meters of each satellite, they began their untethered spacewalk. Allen went first. He flew out to the satellite and attached a capture device that secured it for transport back to Earth. Then Gardner did the same with the second satellite. Footage of the maneuvers looks straight out of a sci-fi thriller.

Despite its success, the MMU was short-lived. After just three missions, NASA retired it in favor of robotic arms and safer, tethered spacewalks. The risk of an astronaut being lost in the void was just too great. 

In the summer of 1950, four men sat down for lunch together at Los Alamos. It was, at the time, the center of American physics, and these men were respected contributors to their field. Among them was Enrico Fermi, a giant in the fields of quantum mechanics and thermodynamics.

But the men were relaxing over lunch, and the conversation was not erudite. Nuclear physicist Emil Konopinski brought up a cartoon he had recently seen in The New Yorker, explaining why public trash cans were disappearing from the streets of New York City. The cartoon showed what was evidently a flying saucer with little green men filing toward it with the spirited-away trash cans.

Well, Fermi pointed out, this was a very logical hypothesis. It explained both the regularity of UFO sightings and the strange disappearance of New York trash cans.

The group laughed and moved on. They finished lunch. Then, out of nowhere, Fermi exclaimed, "But where is everybody?"

He was talking about extraterrestrial life, and everyone at the table knew it. They tossed about some ideas but largely treated the matter as a joke.

"As far as our galaxy is concerned, we are living somewhere in the sticks, far removed from the metropolitan area of the galactic center," said physicist Edward Teller.

But the question stuck. It became known as Fermi's Paradox: if the Earth isn't special, and the Universe is so very big with so many stars, where is everybody?

The search for alien life begins

A decade passed. The Cold War kicked into high gear, driving scientific competition. Radio astronomy historian Rebecca Charbonneau told ExplorersWeb that the Cold War's technological advances spurred the search for extraterrestrial life.

"The launch of Sputnik in 1957 and the subsequent proliferation of artificial satellites — including early signals-intelligence platforms — made detecting non-human technosignatures suddenly plausible," she explained.

The thought of aliens began to captivate a fringe group of astronomers, notably Frank Drake. He convened a meeting on the subject at the National Radio Astronomy Observatory site in Green Bank, West Virginia.

"Drake had invited everyone he could think of with an interest in the scientific search for E.T. — all 12 of them — to the meeting," wrote Nadia Drake, his daughter.

The Drake Equation

In order to guide the discussion, Frank Drake sat down and estimated the number of civilizations in the galaxy with whom Earth could communicate. It was a very simple estimation. The number of civilizations would be equal to the rate of star formation, times the fraction of stars with planets, times the number of habitable planets per solar system, times the fraction of habitable planets that actually lead to life, times the fraction of life-bearing planets with intelligent life, times the fraction of intelligent civilizations that develop a means to communicate in outer space, times how long those civilizations actually release signals.

At the time, astronomers had begun to understand the rate of star formation in the Milky Way. Everything else in the equation was a complete mystery.

When Drake formulated his estimate, astronomers had no confirmation that planets even existed around other stars. All logic suggested they would, but they were far too faint to detect with contemporary telescopes. So the field theorized, argued, and waited.

Astronomers took another two decades to confirm that extrasolar planets, or exoplanets, existed. That confirmation didn't come from any of the famous modern methods of exoplanet detection, such as light fluctuations or watching a star wobble back and forth. Instead, it came from a previous candidate for extraterrestrial communication: the strange dead stars known as pulsars.

Little Green Man 1

The discovery of pulsars dates back to 1967 when graduate student Jocelyn Bell Burnell noticed a strange repeating radio signal in her telescope data. She had no idea what to make of it and dubbed it "Little Green Man 1."

Unfortunately for the little green men, it eventually became clear that the signal came from a rapidly rotating object known as a neutron star. Neutron stars are incredibly dense and incredibly small, with a mass greater than that of the Sun but a radius the size of San Francisco. Every time they spin around, their off-kilter magnetic fields fling out regular radio emissions.

Jocelyn Bell Burnell had discovered the first example of one of the most exotic objects in the known Universe. (The Nobel Prize, of course, went to her advisor.)

The study of pulsars blossomed into a flourishing subfield. In general, pulsars are near-perfect clocks. While different pulsars have different periods, every radio pulse arrives at the Earth perfectly on time.

Not so for the pulsar that Aleksander Wolszczan and Dale Frail observed in 1992. The arrival time of each pulse wobbled up and down: now just before expected, now just after.

First step: finding exoplanets

Wolszczan and Frail tried modeling the noise as a companion star to the pulsar. It didn't work. Every time they succeeded in getting rid of one part of the wobble, another part stepped forward to dominate.

They began thinking outside the box. The best solution was for not one but two companions to the pulsar: planets just a little bit more massive than the Earth. The varying pulse time of arrival came from the pulsar moving back and forth very slightly in its orbit such that each pulse had to travel a subtly different distance to reach the Earth.

Exoplanets existed. Grappling with the first two terms in the Drake Equation was suddenly far more tractable. Onto the next step: How many of the planetary systems out there had habitable planets?

Exoplanets were no longer the domain of the theorists. As the 21st century rolled ahead, new high-sensitivity telescopes allowed the detection of exoplanets around all kinds of stars. Today, we know of almost 6,000.

It took until 2014 for the Kepler satellite telescope to detect anything that looked like Earth. The first such exoplanet is the memorably named Kepler-186f, an Earth-sized planet orbiting at a habitable distance from a red dwarf star. The atmosphere and climate of Kepler-186f differs dramatically from that of Earth, but it's not a stretch to imagine other lifeforms might thrive there.

Nowadays, terrestrial-style exoplanets are so numerous that they comprise an entire subfield. The NASA Exoplanet Encyclopedia tracks all of them, including their mass and how habitable they seem. Statistics of exoplanet habitability are no longer a mystery.

So where's the life?

When Drake formulated his equation in 1961, astronomers had only pinned a value on the first term. Now, the first three are well-understood and understood to be high. In short, there are a lot of stars out there, a lot of those stars have planets, and a lot of those planets are habitable. So where's the life?

For the fourth term (the regularity with which life emerges on habitable planets), astronomers must turn to theoretical estimates by paleobiologists and geochemists. For the fifth (the fraction of intelligent life), evolutionary biologists. The sixth and seventh terms are the realm of theorists doing work that is important but so fringe that they don't have a field to call their own.

The fact remains that, as far as we know, we have never been contacted by any extraterrestrial species. So one of those terms must be exceedingly low, or else something stranger is going on.

Possible answers

Perhaps the simplest way to answer the Fermi Paradox is that life rarely forms in the universe. With the fourth term in the Drake Equation close to zero, humans could expect never to get a call from any nearby neighbors. The nearest extraterrestrial life might be across the Milky Way or in another galaxy entirely. This was the interpretation favored by paleobiologist Stephen J. Gould.

Other biologists posit that the fifth term is the blockade. In this scenario, life abounds nearby, but we're the smartest kids on the block. Astrobiologist Charles Lineweaver points out, "Dolphins have had about 20 million years to build a radio telescope and have not done so."

It's also possible that the sixth term is practically zero. Other intelligent life might exist, but can't communicate with us. Still on about dolphins, Lineweaver adds, "If you live underwater and have no hands, no matter how high your E.Q., you may not be able to build, or be interested in building, a radio telescope."

Those three solutions posit a universe where humans are special. They are also the happiest possibilities. Another common hypothesis is that the seventh term in the Drake Equation -- the length of time for which civilizations communicate -- is very short because natural catastrophes regularly cause the extinction of intelligent life. Asteroids, gamma-ray bursts, and volcanoes are all potential culprits.

A darker theory

The darker version of that theory is that intelligent life inevitably eradicates itself through nuclear war, climate change, or other disasters. Carl Sagan argued that self-destruction was common, but civilizations that avoided it would endure for eons.

"Perhaps there is a waiting time before contact is considered appropriate," he wrote, "so as to give us a fair opportunity to destroy ourselves first, if we are so inclined."

The Dark Forest Theory, named after the book by science fiction writer Cixin Liu, posits that intelligent life wouldn't destroy itself but others. Other science fiction writers such as Dennis Taylor have also flirted with this idea, painting a galaxy in which one species of alien has eradicated most other intelligent life. Stephen Webb suggested that since humans are superpredators, successful alien life would be as well.

It's also possible intelligent alien life exists, but we can't begin to comprehend it. It might not appear as life to us, or as intelligent. It might choose not to communicate for reasons that would baffle us. It might not want to leave its homeworld.

It might, in other words, be alien.

The official "10, 9, 8..." countdown has not quite begun, but later this morning, at 9:46 am ET, Australian polar guide Eric Philips and his three fellow astronauts will blast off into space from Florida's Cape Canaveral aboard SpaceX's Falcon 9 rocket. For the next three-and-a-half days, they will orbit the Earth via the North and South Poles -- an orbital track never done before.

For the 62-year-old Philips, this late-career opportunity came out of the blue. He was guiding a ski tour on Svalbard. One of the participants, Chun Wang, was interested in talking about space. It turned out that Wang had made a fortune in the early years of bitcoin mining and wanted to buy a commercial space flight from SpaceX. He invited Philips to join him, along with two other Svalbard acquaintances, Rabea Rogge and Jannicke Mikkelsen. The cost of the flight is undisclosed, but previous private missions on SpaceX cost around $200 million.

The four of them have been training at SpaceX headquarters near Los Angeles for the past several months. Now, weather permitting, the big day has arrived.

Among their many new experiences, Philips, who wears glasses, has learned to wear contacts for the first time so his glasses won't fog up inside the space suit. However, sometimes myopia temporarily clears up in zero gravity, so he might find that he no longer needs them -- at least for those three-and-a-half days.

You can watch the launch live and follow what they call the Fram2 mission, named after the famous Norwegian polar ship, here.

Before it shut down in 2022, a telescope in Chile captured one final gift for the world that has just been released: the universe's baby photos, just 380,000 years after the Big Bang.

These freckled photos of the early universe, at an instant known as the Cosmic Microwave Background (CMB), are the farthest back in time we can look. Observing the Big Bang or immediately after is not possible, and not just because of technical limitations.

Before the epoch shown in these images, the universe was so dense with plasma that light couldn't travel for more than a fraction of a millimeter without scattering off a proton or an electron. Everything just looked like a dense fog. Then the universe cooled enough to allow those charged particles to fuse into hydrogen and helium. Space opened up and became visible. The last photons from those first visible moments were preserved.

The photons set off through space. All of them were stretched by the expansion of space around them. Some became further stretched out by gravitational wells around galaxy clusters. Others received an energy boost. The patterns of the evolving universe imprinted themselves on these ancient photons.

Almost 14 billion years after their liberation, some of them hit the smooth white surface of a radio telescope located in the Atacama Desert of northern Chile.

Last observations

The Atacama Cosmology Telescope (ACT) is now closed for business. After 15 years of productive data releases, it saw its final light in 2022. However, the ACT team only recently released the polished versions of the telescope's last observations.

These images not only show the most precise, high-resolution observations of the Cosmic Microwave Background but they also cover more of the sky than ever before. The red and blue speckles represent regions of over- and under-densities -- places where, 14 billion years ago, the universe had just a little more or less plasma.

The new images confirm previous observations that the structure in the early universe maps onto its modern structure. Where there were slightly more photons in the primordial plasma now sit the most massive galaxy clusters. Fewer, and there's empty space.

So far, general relativity holds up

Einstein's theory of general relativity, which predicts how matter and light interact with one another at large scales, is one of the best substantiated theories in modern physics. It also causes problems.

There appear to be four fundamental forces in nature: gravity, electromagnetism, weak, and strong. One set of physical laws known as the Standard model cohesively describes electromagnetism, the strong force, and the weak force. Gravity, though, has proven hard to mesh with the others.

Discovering that general relativity isn't quite accurate is the grand hope of those searching for one theory of physics that unites all four forces. Perhaps then, a new model of gravity will appear out of the cracks, one that slots nicely into the Standard model.

But general relativity has triumphed repeatedly so far, and the latest images from the ACT are no exception.

"The amount by which light bends around dark matter structures is just as predicted by Einstein’s theory of gravity," cosmologist Mathew Madhavacheril told Penn Today.

How polarized light fits in the early universe

Perhaps the most important part of these new observations is the detailed polarimetry. Polarimetry describes the measurement not just of how much light there is, or how much energy that light has, but in what direction the light is vibrating. Natural light is unpolarized, meaning that light waves traveling toward us may vibrate in any direction perpendicular to the line of travel.

It's easy to change that by sticking a thin grating in front of the light, only allowing one vibrational direction through. That's how polarized sunglasses work.

The polarization signal in the CMB sits at barely detectable thresholds. But ACT's new observations push past that threshold, and unlike the handful of other telescopes in the polarization game, they cover most of the sky.

Polarization goes beyond the effects of gravity from massive structures like galaxies. Microscopic quantum density fluctuations can alter the polarization of light.

Einstein's formulation of general relativity does not describe the quantum world. In fact, Einstein was uncomfortable with quantum mechanics and encouraged its proponents to better address its many peculiarities. While this leaves room for future physicists to etch their name in history, it would be a lot simpler if Einstein had just figured out everything for us.

He didn't. General relativity on the quantum (read: atomic) scale continues to confound us, not least because testing it in the lab is fiendishly difficult.

Fortunately, the new ACT data release is precise enough to contain clues about quantum gravity in its polarimetry. We just have to decode them.

A team using the telescope atop Mauna Kea in Hawaii has just discovered 128 new moons orbiting Saturn.

Saturn, the sixth planet from the sun, was already the reigning champion of moon-having. A 2023 discovery of 62 new Saturnian moons put it ahead of Jupiter, which takes the silver medal with 95 recorded satellite objects.

Its new count of 274 means Saturn has more moons than every other planet in our solar system combined. This seems rather greedy and possibly bad form.

The wreckage of older moons

The moons were discovered by layering hours of footage of Saturn and adjusting for the planet's own movement. The images showed just enough to know an object was there. The moons themselves are not particularly spectacular, at least not in the pictures we have.

They're blurry chunks of rock of no definite shape or particularly striking colors. These are called "irregular moons" because they aren't neatly spherical like our moon.

But they were born in dramatic circumstances. The little moons are grouped cliquishly together, suggesting that they used to be part of larger moons that split apart. Violent collisions with each other or with passing comets likely broke them into their current small, irregular clumps. In earlier days of our solar system, when orbits were less stable and arrangements less settled, collisions were common.

The destruction of a large moon probably caused the formation of Saturn's other claim to fame — its rings. The rings formed between 100 and 200 million years ago, around the same time that scientists estimate the newly discovered irregular moons were formed.

When is a moon just a big rock?

These small, irregular moons herald coming debates. Telescopes are becoming more powerful, and scientists are developing better methods to analyze images. As this trend continues, smaller and smaller orbital satellites will be found. Are they all moons? How big does a rock have to be before it can be a moon?

The lead researcher, Edward Ashton, anticipates the moon question. "I don’t think there’s a proper definition for what is classed as a moon. There should be."

It will probably be up to the International Astronomical Union to make the call on moon identity. Mike Alexandersen, from the IAU's Minor Planet Center, says that the decision will probably be controversial, like the earlier What is a Planet? debate that led to Pluto's demotion to a mere "dwarf planet."

Naming priority for Saturn's moons will, in the future, go to the largest bodies and those on which craft have landed. For now, none of the 128 new Saturnian moons have names. Most fall within the "Norse cluster," the section of Saturn's orbit with objects named from Norse mythology. The rest, following earlier conventions, will be named for Irish and Inuit mythology. With so many left to name and only so many Norse mythological figures, scientists might have to be flexible.

For now, though, Ashton believes they've found all the moons of Saturn, Neptune, and Uranus, which can be seen with existing telescopes.

This doesn't mean that Jupiter will have a chance to catch up, though. Currently, estimates suggest that Saturn has even more small moons to be discovered with better technology in the future. Jupiter may be the biggest planet in our system, but it will have to be satisfied with second place in the moon department.

Have you ever wanted to see Earth through the eyes of the astronauts? NASA’s Gateway to Astronaut Photography of Earth is an incredible catalogue of images that allows you to do just that. It offers a new perspective on our planet, captured by astronauts aboard the International Space Station (ISS) and on past space missions. 

This searchable online archive features over 1.8 million photos of the Earth taken over the last seven decades. 

Search image categories

Using the search tool, you can explore images by location, mission, or collection. For example, you can look up high-altitude overviews of your city or your favorite landmarks. You can choose specific categories such as Volcanoes, Earth Art, Mission Highlights, or watch time-lapse videos.

This is so much more than a collection of amazing photos. Astronauts are trained to capture images for scientific studies, and the Crew Earth Observations (CEO) track environmental changes, monitor natural disasters, and study how human activity affects the planet.

Astronauts on the ISS work with land-based scientists to target key regions. Orbiting at 354km to 460km above our planet, the ISS offers an unparalleled platform. Every image includes location details and camera information and is free to download. 

Space is full of surprises, and the most recent of these is: Spirals are the solar system's favorite shape. Astronomers have uncovered a surprising spiral structure at the edge of our solar system that closely resembles the distinctive shape of our Milky Way. 

The discovery was made using NASA's Pleiades supercomputer. It simulated the behavior of the Oort Cloud — a vast, spherical shell of icy bodies at the edge of our solar system, beyond view. It is so remote that even NASA's Voyager 1 spacecraft, traveling at about 1.6 million kilometers per day, won't reach it for another 300 years.

The Oort Cloud is home to countless frozen bodies that occasionally get knocked toward the inner solar system, becoming the comets we see streaking through the sky. But until now, no one suspected these objects sit in a spiral pattern. Astronomers have generally thought of the Oort Cloud as a random collection of icy bodies. 

Unfathomably huge

The simulations indicate that the inner region of the Oort Cloud forms the spiral structure, much like the spiral arms of the Milky Way. This spiral spans approximately 15,000 astronomical units (au) in length. One au equals 150 million kilometers, the distance between our planet and the Sun. So 15,000 of those is unfathomably large.

"We found that some comets in the inner Oort Cloud, found between 1,000 au to 10,000 au, form a long-lasting spiral structure," Luke Dones, a co-author of the new study, told Space.com. "We were quite surprised. Spirals are seen in Saturn's rings, disks around young stars and galaxies. The universe seems to like spirals! Only a small fraction of comets in the Oort Cloud are in this spiral, but that's still billions of comets."

Why the solar system favors spirals is a mystery. Scientists believe the structure could be due to the complex gravitational influences of the galaxy, passing stars, and even the movement of the solar system itself as it orbits the Milky Way. However, we're a long way from understanding all the forces at play well enough to explain the tendency for spirals to form.

It came from the Oort Cloud, a giant web of floating miniature planets lying just beyond the edges of the solar system. It dazzled the skies above Chile for a handful of weeks. Now it's gone for the next 600,000 years.

The Oort Cloud

The Oort Cloud, technically, isn't a confirmed place. It's a theoretical location. Some comets orbit the Sun over hundreds of thousands or even millions of years. They must, therefore, call somewhere home. That place is the Oort Cloud, a massive reservoir of icy comets lying outside the boundary of the solar wind, too far for telescopes to see.

Many famous comets return within a generation. Halley's Comet, for instance, will visit again in 2061. But when comets head in from the Oort Cloud, they won't be back anytime soon.

Early observations of the comet

Way back in April of 2024, observers at a small telescope in Chile reported a very faint speck hurtling toward the Sun. It was a comet, the icy siblings of asteroids, and it was 655 million kilometers away but approaching rapidly.

It took the name of the observatory that discovered it -- ATLAS. And as 2024 turned to 2025, amateur astronomers started reporting that ATLAS was visible with the naked eye at night. Instead of a little dot barely visible with a telescope, it was now as bright as Polaris, the North Star.

This sudden increase in brightness was caused by the disintegration of the comet's surface. As the comet sped towards the Sun, the temperature increase evaporated large chunks of ice from its surface, feeding its outgassing tail and the hazy glow around its nucleus. But in early January of 2025, it hadn't yet reached its full glory.

The Great Comet of 2025

On January 13, ATLAS entered an exclusive club: the list of comets within the last century that were visible to the naked eye during the day. At the time, it was passing through perihelion, the closest approach to the Sun. It was brighter than anything else in the southern sky, including the planets.

Astrophotographers snapped stunning photos of its tails, one comprised of heavy particles and the other of light gases. An astronaut on the ISS snapped a photo of it through the space station windows. And NASA used a telescope device called a coronagraph to block out the Sun's light, allowing sensitive cameras to observe the comet without being blinded.

Goodbye, ATLAS

ATLAS is heading away from us, but not unscathed. On January 19, the bright little speck of its nucleus vanished, suggesting that the comet fragmented after its passage around the Sun. What's left is a ghost: tails still streaming across the sky in the wake of debris that soon may disintegrate entirely. We'll have to wait half a million years to see if any part of it survived its vacation to the center of the solar system.

For the fourth year in a row, NASA's Curiosity rover has photographed iridescent clouds drifting across the Martian sky. The clouds appear in the same place, at the same time of year.

On January 17, during the early Martian autumn, Curiosity's Mastcam recorded these noctilucent, or "night-shining," clouds for 16 minutes. The Sun's rays scatter against the clouds, creating colorful, "mother-of-pearl" clouds tinged with red and green.

Cloudgazing... on Mars!
@MarsCuriosity captured these colorful clouds drifting across the Martian sky. The iridescent, carbon dioxide ice formations offer clues about Mars' atmosphere and weather: https://t.co/HAp2FDFjhk pic.twitter.com/DEWV477X01

— NASA (@NASA) February 11, 2025

Dry ice clouds

Regular Martian clouds are composed of water ice, but researchers believe that frozen carbon dioxide, or dry ice, makes up the noctilucent clouds. They float 60 to 80 kilometers above the surface of the Red Planet, where frigid temperatures cause the carbon dioxide to condense into colorful, wispy clouds. Some plumes descend to 50 kilometers before evaporating in the rising temperatures.

Twilight clouds on Mars were first observed during NASA's Pathfinder mission in 1997. Curiosity's recent observations mark the fourth time that these iridescent clouds have appeared over the Gale Crater in the planet's southern hemisphere. They seem to come at the same time each year.

This predictability has allowed scientists to plan their observations meticulously. Mark Lemmon, an atmospheric scientist at the Space Science Institute, recalls his initial encounter with these clouds: "At first, [I was sure] it was some color artifact…Now it's become so predictable that we can plan our shots in advance."

Strangely, the twilight clouds do not seem to form anywhere else on the planet. One hypothesis is that atmospheric gravity waves help generate the clouds. The waves cool the atmosphere and create cool enough conditions for the clouds to form.

This is, however, just a theory. “Martian gravity waves are not fully understood and we're not entirely sure what is causing twilight clouds to form in one place but not another," says Lemmon.

Last week, the world was obsessed with an asteroid that had a 3% probability of hitting us in 2032. Now NASA says it doesn't have a chance in 50,000. What happened?

How are impact probabilities calculated?

I wrote last year about how potentially hazardous asteroids are detected. One aspect I neglected is what that "impact probability" actually means. In the wake of the news about 2024 YR4 and its rapid upgrading and downgrading of threat, I've gotten a lot of questions about how reliable our asteroid observations actually are.

The answer: very. When asteroid hunters first detect that little moving dot against a stationary sky, they have only a handful of data points. Uncertainty will mar any measurements they make of the asteroid's position and velocity.

It's that uncertainty that defines impact probability. Astronomers calculate the trajectory of the observed asteroid, allowing room for error. If that trajectory passes anywhere near the Earth, then as long as the error bars are substantial, the impact probability is as well.

Why did the impact probability go up first?

Once asteroid hunters spot a potentially hazardous asteroid, telescopes around the world jump to observe it, reducing the uncertainty about its trajectory.

But if the asteroid is still heading anywhere near the Earth, the smaller error bars increase the probability of an impact. That's what brought YR4 into the public eye.

This is a pattern with asteroid impact probabilities. An asteroid starts with a moderate possibility of impact. Astronomers jump to observe it, decreasing the uncertainty but not yet ruling out a collision with the Earth. The impact probability jumps up.

Then the error bars on the orbit shrink even further, and suddenly they no longer encompass the Earth. The impact probability drops to pretty much zero.

Asteroid 2024 YR4 hasn't suddenly started behaving less chaotically. We just understand it better, and know exactly where it's going to go. And that's not the Earth.

Intuitive Machines, which became the first private company to land on the moon in February of 2024, is planning its second landing. This time, they will bring something new: a 4G LTE wireless network.

Working with Nokia, with funding from NASA, the mission will feature a “network in a box” attached to the side of Athena, the mission lander. Athena will land in the south polar region of the moon, near the Shackleton Crater. Then, it will deploy several rover vehicles to explore the surface and take samples. The rovers will connect to Athena’s wifi and relay data back in real time.

Connectivity issues

I can’t get reliable internet in my flat in Dublin. How much more difficult will it be to set those systems up on the moon?

Temperature extremes on either end can damage equipment and degrade performance. The lunar surface can be as hot as 121˚C in daylight and plummets to -246˚C inside the Shackleton Crater. Even for the polar explorer after whom the crater is named, that is excessively cold. The lunar soil is also rough, with small jagged pieces which can scratch and damage materials.

The challenges of the lunar surface are only relevant if the equipment can even make it to the Moon. Athena faces a 385,000km journey, and the jostling and extreme forces involved in launching, flying, and landing will put the toughest materials to the test.

The upside is that the advancements made for Moon wifi might in turn improve our Earth wifi, possibly allowing me to stream video at a higher resolution than 144p.

The LSCS

The box Athena will carry is Nokia’s Lunar Surface Communication System (LSCS). Nokia designed the technology specifically for space travel and for Athena. Fourteen separate thermally isolated mounting points should protect the delicate machine from the extreme temperatures of space and keep it snugly attached.

The rovers that will connect to the LSCS wifi are called Mobile Autonomous Prospecting Platform (MAPP). Another one is called Grace -- that team had more fun with it, I guess. MAPP will travel the south polar regions, mapping and collecting images and environmental data.

Meanwhile the mission will use Grace (also known as Intuitive Machine’s Micro-Nova Hopper) along with the LSCS to test new sensory systems while exploring the permanently dark, cold craters.

The company aims to launch the Athena lander from NASA’s Kennedy Space Center at the end of February. It will land in the same neighborhood targeted by NASA’s upcoming manned Artemis mission. No word yet on whether the Artemis astronauts will be given the wifi password when they get up there.

Around 13.7 billion years ago, something collapsed. It fell outward into the nothingness that stretched in every direction, leaving something behind. A dense plasma, made of fundamental particles called quarks and gluons. For one tiny moment, the plasma collapsed outward unimaginably fast. Then, reigned in by the quarks coalescing into matter, the collapse began to coast.

The universe cooled. Small clumps of matter, set by random chance in the first moments of its existence, attracted more matter through gravity. They became gas clouds, and then galaxies. Galaxies formed galaxy clusters. And empty space continued to expand.

This was the Big Bang, and it set off the expansion of the universe. Today, we'll look at the strange forces that drive the acceleration of its expansion, as well as one of the most tantalizing open questions in modern astronomy: Exactly how fast is it expanding today? And why can't we figure that out?

The expanding universe

In 1929, an astronomer named Edwin Hubble found that every single galaxy outside of the Local Group -- our neighbors -- was speeding away from us. Galaxies like Andromeda, our nearest large neighbor, had stars that looked more or less the same color as the ones in the Milky Way. But beyond that, every galaxy looked red.

This, Hubble reasoned, was because of the Doppler effect. When a fire truck is driving away, its siren sounds like a decrescendo because the outgoing velocity stretches out the sound waves. The chances of every galaxy outside our local sphere of the universe being naturally red were small. Hubble concluded the simplest explanation was that every galaxy was moving away from us.

At first glance, this implies there is something special about the Earth. But one of the principles of cosmology, the study of the birth, death, and overall structure of the universe, is that there are no special locations. Any galaxy perceives all distant galaxies as moving away. This is because the space in between galaxies is expanding with every passing second.

In 1998, a team of cosmologists observed the recession velocities of distant galaxies and noticed something strange. At very high distances, galaxies were even further away than they should have been if the velocity was constant. That meant the universe hadn't expanded at a constant rate.

Instead, it's accelerating over time.

Introducing dark energy

According to Newton's first law, objects in motion will stay in motion unless acted on by an outside force. Once galaxies were moving apart from one another due to the Big Bang, therefore, it made sense for them to continue on their trajectories. But for the universe to be accelerating meant that a force was driving that acceleration.

Astronomers dubbed this new factor dark energy, because they didn't know what it was. It's still perplexing, but in the decades since, dark energy has become accepted as part of the universe's source code. Mass attracts mass, like-magnets repel one another, and empty space naturally expands.

Dark energy says: you can't have a true vacuum. Seemingly empty space actually has natural energy, and it wants to get out. It expands -- and if it's already expanding, that expansion accelerates.

The Hubble Tension

So if the expansion velocity of the universe isn't always the same, what is its present value?

For modern cosmologists, the answer to that question is a Holy Grail. It's not that we have no idea. We have too many ideas. Over and over again, the same two values keep cropping up: 67 km/s and 73 km/s.

In the past, astronomers like Edwin Hubble didn't realize the expansion was accelerating because their observations didn't reach far enough, and when they did, they weren't very precise. But over the last two decades, astronomers have developed very sophisticated techniques for measuring the expansion of the universe. About half of those techniques give a modern expansion velocity of 67 km/s, and the other half give 73 km/s.

At first, cosmologists assumed the values differed because the measurements weren't precise enough. The error bars covered the whole range of values between the two limits, so there was nothing to worry about.

Then the measurements got better and better, the error bars shrank, and still the two values stayed separate. Why?

Cosmic Microwave Background

The further away we look, the further back in time we look. That's because light takes time to travel toward us, so the light from very distant parts of the universe reaches us billions of years after it was emitted. As we look back, we see modern galaxies, then middle-aged ones, and then the strange clumpy squiggles of very ancient galaxies. Then we see the wall.

It's not a physical wall. Instead, it's the image of a time when everything in the universe was on fire. It's called the Cosmic Microwave Background, or CMB. It formed when protons and electrons merged into atoms, suddenly releasing the photons from ricocheting around the primordial plasma. Those photons have been traveling ever since, and are reaching us every day. Part of the static on any radio station or television screen comes from the earliest observable light in the universe.

The CMB isn't perfectly identical in every direction. It has clumps and divots, and those ancient clumps and divots laid the blueprint for the distribution of galaxies in the modern universe.

Cosmologists plug the attributes of those clumps into a general relativity model of the universe starting at the Big Bang. When the clock reaches the present day, the universe is expanding at about 67 km/s.

Wobbling Cepheids

So far, general relativity has withstood every test that's come its way. Why is it, then, that its predictions for the current expansion velocity from the CMB don't match our observations from galaxies?

Figuring out the current velocity from galaxies requires knowing how far away those galaxies actually are. Astronomers use something called the cosmic distance ladder to connect observations within our own galaxy to observations in other galaxies.

First, they observe nearby stars called Cepheids. Cepheids don't have a constant brightness. Instead, they get periodically dimmer before brightening again. The brighter a Cepheid is, the faster its light fluctuates. By observing how fast they fluctuate, astronomers can calculate how bright a Cepheid in another galaxy really is, instead of just how bright it looks when viewed from far away. That gives the distance to the galaxy.

Every so often, two orbiting white dwarfs in these galaxies collide, leading to a massive explosion called a Type 1a supernova (supernova astronomers are infamous for their opaque naming conventions).

Using the known distance of the galaxies, astronomers figured out that the peak brightness of these supernovae controls how fast the light fades. So if a Type 1a supernova goes off in a distant galaxy, we know from the light decay speed how bright it should appear. Once again, we can extrapolate the distance of the galaxy based off how bright its most exotic stars actually appear.

Finally, the Doppler effect allows us to calculate recession velocity of those galaxies. It's always about 73 km/s.

What causes the Hubble Tension?

The discrepancy between these two measurements is called the Hubble Tension, and it doesn't seem to be going away. Other methods of calculating distance from galaxies -- microwave lasers and neutron star mergers, for instance -- give the same result as the supernovae of 73 km/s. Meanwhile, no matter what methods are used to calculate the expansion velocity from the CMB, they all give 67 km/s. A handful of measurements fall somewhere in between, but the vast majority pick a side and stick to it even as their error bars shrink.

It's not clear what's going on. The universe can't be expanding at both 67 km/s and 73 km/s at the same time, so we're going wrong somewhere. Is there some recurring error in how astronomers are calculating distance of galaxies? Are the CMB measurements not as accurate as we think?

Why don't observations in the recent, galaxy-inhabited universe give us the same answers as observations from the very beginnings of the universe. And which of the answers is correct?

Anyone who can answer that question is practically guaranteed a Nobel Prize. But right now, cosmologists have no idea.

The dominant theory is that dark energy was stronger in the early universe in a way the models don't take into account. That would mean that no matter how precise our CMB measurements are, our models aren't correctly extrapolating that information to the present day. But if that were the case, why would dark energy change over time? Isn't it supposed to be a constant of the universe?

There are other, more outlandish theories involving strange "dark" photons that have pushed the modern universe into an increased expansion velocity. But the most disconcerting prospect is not the existence of yet another strange physical substance with "dark" in its name: it's the idea that our model of gravity itself is somehow fundamentally flawed. If so, the story of the universe will have to be rewritten.

At the end of January, scientists gave Asteroid 2024 YR4 a 1 in 83 chance of colliding with Earth in 2032. Those odds have now almost doubled to a 1 in 43 chance.

To learn more, the James Webb Space Telescope has been tasked to observe the space rock before it disappears from view for several years.

The chances of the asteroid colliding with Earth are still incredibly low -- just 2.3%. However, that still marks the biggest asteroid threat in over two decades. Based on ground telescope data, scientists estimate its size at 55 meters in diameter. That's big enough to take out a city. However, it is possible that the asteroid is much larger.

"In general, the brighter the asteroid, the larger it is, but this strongly depends on how reflective the asteroid's surface is. 2024 YR4 could be 40m across and very reflective, or 90m across and not very reflective," European Space Agency (ESA) officials pointed out recently.

To better estimate its size, which is the key metric of how much damage a collision might cause, the JWST will analyze the heat coming from the asteroid using infrared technology. Researchers will also study its route and surface composition.

Even with the JWST, astronomers can view the asteroid only at two points in its trajectory — in March and May. After that, it slips out of view until 2028.

However, that is not the only limiting factor. The team can use the space telescope for just four hours in total. The telescope is in high demand, and every minute on it is stringently scheduled and budgeted for, even for important uses like this one.

Albert Einstein predicted in 1912 that massive objects should bend light as it passes through their gravitational field. He published his theory of general relativity four years later, and the curvature of light seemed a minor point at the time.

When Russian physicist Orest Khvolson posited that in rare cases, the bending of light would create a halo effect, Einstein acknowledged this but wrote, "Of course, there is no hope of observing this phenomenon directly."

Einstein, for once, was wrong. This week, a team from the European Space Agency's dark energy survey telescope Euclid published a high-resolution photo of a halo effect called an Einstein ring. And unlike previously observed Einstein rings, this one is from a nearby galaxy.

Einstein rings show distant galaxies

While the math of Einstein's theory of general relativity may be complex, the core principle is not. Gravity, Einstein argues, is best described as the warping of space around massive objects. There's a common analogy demonstrated in science museums, where guests can roll a penny (or other undesired coinage) down the sides of a funnel and watch as it orbits inexorably downwards. Planets perform the same dance in space distorted by the Sun's gravity.

In this framework, light bending around massive objects is a logical outcome. The space around those objects warps like a funnel, and light curves in an arc around the center.

This effect is called gravitational lensing. Einstein rings appear when the lensed image lies right behind the object that's doing the lensing. Because nothing on Earth or even in the Milky Way is massive enough, all the Einstein rings we observe are formed when the light from distant galaxies contorts around more nearby galaxies.

A uniquely nearby Einstein ring

The Einstein ring imaged by Euclid is one of the closest to home ever found. The lensing galaxy is only 590 million light-years away, or just over 200 times as distant as the Milky Way's nearest galactic neighbor Andromeda. In fact, astronomers have known of this galaxy's existence since 1884, before they even knew that galaxies lay outside the Milky Way. Meanwhile, the galaxy that's being lensed is a lot further -- a whopping 4.42 billion light-years away.

The clues hidden in Einstein rings

Previously, Einstein rings have given cosmologists -- astronomers who study the evolution of the universe -- key information on early galaxies. Our telescopes have a long way to go before they can detect the earliest galaxies whose light is reaching us. But when that light passes through a gravitational lens, more of it focuses on us. If we're an ant on the sidewalk, then the lensing galaxy is a kid with a magnifying glass.

That means that our only direct observations of very early galaxies come from lenses like Einstein rings. Cosmologists use them to understand what kind of stars existed in the early universe.

But Einstein rings also provide a lot of information about the galaxy doing the lensing. How massive are they? How is that mass distributed? And how much of it comes from dark matter versus ordinary stars and gas?

In this case, the Euclid team found that the lensing galaxy has more massive stars at its center than the Milky Way does. Massive stars are the rarest, numbering 1 for every 25,000 Sun-like stars. Astronomers still don't understand all the factors that lead galaxies to form certain types of stars. This Einstein ring adds another piece to the puzzle.

If an alien civilization exists and has technology similar to ours, could it detect human life on Earth from a distance? If so, how close would it need to be?

Recent studies from the SETI (Search for Extraterrestrial Intelligence) Institute explore these questions in the hope that they may in turn help us detect alien life.

Researchers, led by Sofia Sheikh, have been examining various "technosignatures" -- indicators of advanced technology -- to understand how visible our planet might be to alien observers. They believe radio transmissions, particularly those from planetary radar systems, are the most detectable.

The powerful radio wave could be observed up to 12,000 light-years away. This means that a distant alien civilization with technology like ours would be able to identify Earth as a planet with an advanced civilization.

"Our goal with this project was to bring SETI back 'down to Earth' for a moment and think about where we really are today with Earth's technosignatures and detection capabilities,” said co-author of the study, Macy Huston. “In SETI, we should never assume other life and technology would be just like ours, but quantifying what 'ours' means can help put SETI searches into perspective."

Pollution is the 2nd most visible sign of humanity

Ironically, the next most detectable technosignature after radio waves is atmospheric pollutants. Markers of industrial activity, such as nitrogen dioxide (NO₂), are emitted from our atmosphere and can be detected up to 5.7 light-years away. To pick up such emissions, extraterrestrial civilizations would need telescopes as powerful as the James Webb Space Telescope and the upcoming Habitable World Observatory.

As the hypothetical alien observers approach closer to Earth, more and more signs of life would be detectable. City lights from urban areas and the thermal signatures of cities become visible. Advanced extraterrestrial telescopes could even detect satellites and space debris orbiting the Earth.

These many signals make Earth's civilization fairly visible to anything out there that is looking for signs of life.

Understanding Earth's technosignatures also guides our own search for extra-terrestrial life. By identifying which signals are most detectable, researchers can better anticipate what to look for on exoplanets. This approach enhances the strategies employed in SETI, potentially bringing us closer to discovering intelligent life beyond our planet.

Space agencies have spotted an asteroid that could collide with Earth on December 22, 2032. An automated telescope in Chile discovered the asteroid named 2024 YR4 this past December.

It is now at the top of the impact risk list, but the odds of an actual collision remain fairly low. According to astronomers' calculations, it has a 1 in 83 chance of actually hitting us.

At 55 meters wide, 2024 YR4 is relatively small. For comparison, the asteroid that wiped out the dinosaurs was nearly 15 kilometers in diameter. But despite its modest size, it could still pack a punch if it defied the odds and struck the Earth. The rock's speed and mass would unleash eight megatons of energy -- 500 times more than the atomic bomb dropped on Hiroshima. It wouldn’t wipe out all humanity, but it could destroy a major city.

'Merits attention'

Currently, the asteroid has been ranked a three on the Torino Impact Hazard Scale, which measures the risk of space objects colliding with Earth. A rating of three “merits attention” in astronomer-speak. According to this scale, “Current calculations give a 1% or greater chance of collision capable of regional devastation.”

2/ The clip below shows ESO’s VLT recent observations of asteroid 2024 YR4, which have helped refine its trajectory. It is estimated to be 40-100 m wide, but more data and analysis are needed to confirm the size, and to refine its trajectory.

ESO/O. Hainaut et al.

[image or embed]

— ESO (@eso.org) 29 January 2025 at 17:01

Astronomers will closely track 2024 YR4 over the next few years. The asteroid is currently moving away from us, and it won’t be observable again until 2028. Until then, it’s likely to remain at Level 3. When it comes back into view, more precise measurements will help scientists determine whether it poses any real danger.

While a 1 in 83 chance of impact sounds alarming, history has shown that such odds for asteroids often change as more observations refine their trajectories. Though most expect its risk level to drop to Level 0, asteroid response groups have been alerted and will keep tabs on it.

Astronomer Colin Snodgrass told The Guardian, “The first step in the planetary defense response is...further observations. If these don’t rule out an impact, the next steps will be more detailed measurements using telescopes and discussion of what space agencies could do in terms of more detailed reconnaissance and eventually mitigation missions."

If the space rock is making a beeline for Earth, for example, one possible strategy is to nudge it off its course with a spacecraft. This technique was successfully tested in 2022 with NASA’s DART mission.

For now, scientists stress that there is no cause for worry. The chances of an eventual collision remain low, for now.

NASA's Curiosity Rover has discovered that the Martian surface was once mild enough for liquid water. In 2022, it found ripples in rock in the Gale Crater that resemble the wave patterns on a sandy lake bed on Earth.

We already know that ice exists at the planet's poles and that its thin atmosphere contains water vapor. We even know of ancient frozen lakes. Last year, NASA’s Insight lander discovered reservoirs of liquid water ten kilometers deep inside the Martian crust.

But never before have we seen that surface liquid water once existed on Mars.

“The shape of the ripples could only have been formed under water that was open to the atmosphere and acted upon by wind,” said Claire Mondro, lead author of the new study.

Around 3.7 million years ago, the climate on Mars was above freezing. The Rover discovered two sets of ripples, which are just six millimeters high and four to five centimeters apart. To learn more about the ancient lake, researchers combined the ripple measurements with computer modeling. It turns out that the lake was quite shallow, around two meters at its deepest point.

Did life exist, too?

This discovery contradicts the assumption that the planet was cold and arid during that era. It also means that Mars once had a much thicker atmosphere, capable of retaining heat. This means Mars also had more scope to harbor microbial life.

The ripples happened when the planet was becoming drier, and the two sets also formed at different times. This means that either the planet was warm enough to have liquid water for far longer than expected or that a denser atmosphere existed more than once in the planet's history.

"Extending the length of time that liquid water was present extends the possibilities for microbial habitability later into Mars history," Mondro said.

Understanding the planet's climatic history and the role of liquid water is crucial for assessing Mars's habitability and guiding the ongoing search for past life

We know more about the universe than many people think.

Space mysteries are usually quite mundane to all but obsessive researchers. The most compelling open question in astrochemistry, for instance, is how often molecules are recycled during star formation before depositing onto the surface of planets. It's a key gap in our understanding of outer space environments, but it's not going to intrigue any first dates.

But there are a few tantalizing questions that are so big we can't even tackle them head-on. Questions that most astronomers hope against hope will be answered in our lifetime -- but deep down don't believe ever will be.

In this new series, we'll cover some open questions in astronomy, starting relatively small and working our way up. This week: the mysterious, sometimes-repeating extragalactic signals known as Fast Radio Bursts.

An accidental discovery

In 2007, a grad student at West Virginia University -- arguably the center of American radio astronomy -- found a strange whooping signal in old telescope observations. It started at high radio frequencies and, over the course of half a second, swept down to low. Then it disappeared.

The high-to-low-frequency aspect wasn't a mystery. That sweeping pattern appears all over radio astronomy because the free electrons floating around interstellar space slow down low-frequency light more than high-frequency light. Since it gets delayed more, it shows up at the telescope a moment after the high-frequency parts of the signal.

We see this all the time in radio signals from within the Milky Way. We know about how many free electrons there are floating around in our galaxy and how much they delay different frequencies of light. Therefore, the degree of delay from electrons is often used as a rough measure of the distance of an object.

The signal that grad student Ash Narkevic had just found was so delayed that it could only have come from another galaxy.

The Lorimer Burst

Narkevic's advisor was an up-and-coming professor of transient radio astronomy named Duncan Lorimer. He and Narkevic wrote a paper about their discovery, submitted it to the prestigious journal Science, and were soundly rejected.

They resubmitted. This time, their paper was accepted. The world of radio astronomy collectively lost its mind and began pouring over archival data, searching for similar bursts.

They found nothing. In fact, they found worse than nothing. In 2011, after four years of radio silence, a graduate student at WVU named Sarah Burke-Spolaor found a signal that looked uncannily like Lorimer's burst. She called it a peryton. The trouble was, it was so bright that it could only have been produced on Earth. Had the Lorimer burst, fainter though it was, also been created on Earth?

Furbies

The mystery remained for another two years until a PhD student at the University of Manchester named Dan Thornton turned his eye to a set of data with very precise time information. His search found four more bursts just like Lorimer's. The bursts were real, and at the suggestion of the Manchester team, they earned a name: fast radio bursts, or FRBs.

There was some early discussion on whether this should be pronounced "furbies," but the consensus was that this would make radio astronomers look silly. And FRBs are very serious indeed.

Microwave oven?

With new advances in observing using very precise time-processing software, the FRBs started pouring in. The one found by Ash Narkevic in 2007 hadn't traveled far compared to some of the new FRBs. One of them seemed to have been created 7 billion years ago.

But a specter hung over FRBs. The too-bright peryton signal found by Sarah Burke-Spolaor still lurked in the backs of everyone's mind, taunting them with the question: If these things look so similar, and some of them are definitely terrestrial, are all of them?

Then, in 2015, an experiment at the Murriyang radio telescope in Australia vindicated FRBs. Swinburne University graduate student Emily Petroff, long obsessed by the puzzle of perytons and FRBs, published the solution in probably the funniest non-joke paper ever written in radio astronomy.

The existence of obviously terrestrial perytons "had previously cast a shadow over the interpretation of [FRBs], which otherwise appear to be of extragalactic origin," she wrote. "We have identified strong out-of-band emission at 2.3–2.5 GHz associated with several peryton events. Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely, and the telescope is at an appropriate relative angle."

FRBs had nothing to fear: "We furthermore demonstrate that the microwave ovens on site could not have caused [the Lorimer Burst]."

The identity of perytons is a continued point of amusement among radio astronomers, and was even parodied in an xkcd panel.

The clues

For once, xkcd made a science mistake. In the comic strip, they describe the origin of FRBs as "stellar-sized objects." We know this can't be true. The time between the start and the end of many bursts is so short that light could only travel a distance of ten or so kilometers during them. Since light is the fastest thing in the universe, points not connected by light wouldn't know to emit at the same time. The bursts, therefore, are created within roughly the distance from Everest to Makalu.

Stars are a lot bigger than that.

Another clue in the FRB toolbox, discovered in 2015: Some of them repeat. The pulses look different every time, but they're very clearly coming from the same location and the same distance. Many more have only ever been seen once. So unless there is more than one mechanism creating FRBs, they aren't produced by one-off events like supernovae or two stars merging.

The magnetar explanation

And then there's the final clue. In 2020, independent teams at Caltech and at the CHIME telescope in Canada both found what looked like an FRB coming from an exotic object within the Milky Way called a magnetar. It was 30 times fainter than the faintest FRB but offered a tantalizing explanation.

Magnetars (Lead image) are the corpses of stars that can no longer support their own weight. Gravity crushes them until their protons and electrons squeeze together to form neutrons. They have massive magnetic fields and regularly send out brilliant flashes of gamma rays and X-rays -- high-energy photons that often go hand in hand with radio waves. In fact, the Caltech team found that the magnetar released X-rays at the same time as the FRB-lite.

The mystery

So magnetars produce FRBs somewhere on their surface via hijinks in their magnetic fields. Mystery solved.

Except that picture doesn't explain many extragalactic FRBs. Gamma-ray and X-ray bursts from magnetars are very rare, so how could so many FRBs repeat monthly or even weekly? And why do some FRBs come from galaxies where we don't expect to find any magnetars? After all, magnetars are all born early in a galaxy's life span. They only stay magnetized for about 10,000 years. Meanwhile, an FRB reported just this month came from a galaxy that's been around for 11 billion years.

At this point, astronomers know only one thing for sure: FRBs aren't coming from microwave ovens.

Anymore.

New research backs up the old hypothesis that the key ingredients for life may have come to Earth on an asteroid billions of years ago. A modern case in point: The asteroid Bennu contains all the materials needed for life.

The OSIRIS-REx mission launched in 2016. Its main aim was to study Bennu and retrieve samples to bring back to Earth. The spacecraft reached Bennu in 2018 after traveling 320 million kilometers from Earth. It spent two years mapping its surface, then collected a 120g sample before landing back on Earth in 2023. Since then, scientists around the world have been unraveling its secrets.

Asteroids like Bennu are essentially time capsules, revealing the chemical makeup of the early solar system. Meteorites undergo significant changes when they enter the Earth’s atmosphere before crashing into its surface, but the material from Bennu is completely uncontaminated. Researchers have never seen anything like it before.

“There were things in the samples that completely blew us away,” said Sara Russell, co-author of the study. "The combination of the molecules and minerals preserved are unlike any extraterrestrial samples studied before."

Bennu’s samples contain amino acids, minerals containing water, and complex carbon structures. The presence of hydrated minerals suggests that Bennu once even had liquid water. Scientists have identified 14 out of the 20 amino acids used by organisms on Earth to build proteins and the four nucleotide bases that we see in DNA.

Far-reaching implications

“What we’re seeing in these samples is a unique combination of minerals and organic molecules that are unlike anything we’ve encountered in previous meteorites," says Russell. "This suggests Bennu and similar asteroids played a crucial role in delivering materials that could have supported the origin of life.”

The discovery of life’s essential ingredients in Bennu’s material has far-reaching implications. It is likely that similar asteroids also delivered these building blocks of life to other planets and moons within our solar system. Mars, Europa, and Enceladus, in particular, have water and organic molecules.

"The early Solar System was really turbulent, and there were millions of asteroids like Bennu flying about," said co-author Ashley King.

Cell phone dead zones in the U.S. took another step toward oblivion yesterday. T-Mobile and Starlink are now beta-testing their direct-to-cell satellite texting capability for iPhones.

The T-Mobile Starlink system uses some 300 Starlink satellites to provide coverage across parts of North America that have historically been empty of cell signals. Essentially, the Starlink satellites function as mobile, orbiting cell towers.

The Federal Communications Commission (FCC) approved the partnership in November of last year, and T-Mobile announced shortly thereafter that iPhone-using customers could register for the test. Earlier in the fall, the FCC had granted temporary approval for Starlink and T-Mobile to put the system into action when parts of Western North Carolina lost cell signal during Hurricane Helene.

According to T-Mobile's website, voice and data capability will soon follow. The direct-to-cell beta-test capability rolled out with the iOS 18.3 software update.

It's big news for the adventure world. Currently, outdoor aficionados who want to stay in contact via their phones have to use third-party satellite messaging devices or dedicated satellite phones. One less gadget to carry around is always a good thing, assuming you are the type of person who likes to stay in contact.

While the initial Beta test is only taking place in the U.S., it's just a matter of time before the program expands to other countries.

Of course, there is a downside. The increasing number of Starlink satellites streaking across the night sky is a serious bother for astronomers and scientists attempting to learn more about our cosmos.

Few of us are lucky enough to catch a glimpse of the Northern Lights from below. Seeing them from the other side around — that is, from orbit — well, that's a rare treat reserved for space farers.

NASA astronaut Don Pettit got a chance to do just that on January 6 as the International Space Station flew above the Aurora Borealis on January 6. Luckily for you and me, he recorded the display and posted the video to X.

The ISS orbits the Earth at an altitude of about 412 kilometers. Meanwhile, the green shades seen in the video are the result of discharged solar particles interacting with oxygen hovering 120 to 180 kilometers above the planet's surface.

It's just a nine-second clip, but you'll probably watch it six or seven times. I know I did.

Flying over aurora; intensely green. pic.twitter.com/leUufKFnBB

— Don Pettit (@astro_Pettit) January 6, 2025

Gaia has completed the mapping phase of its mission. Since its launch in 2013, the European Space Agency’s Gaia spacecraft has been charting our galaxy one star at a time. In those years, Gaia achieved a monumental feat, creating a three-dimensional map of over two billion stars across the Milky Way. 

Now, the top-hat-shaped spacecraft is nearing the end of its journey. After 10 years, Gaia’s fuel tank is almost empty. It has been using 12 grams of cold gas fuel daily to keep it spinning. According to the ESA, “This amounts to 55kg of cold gas for 15,300 spacecraft ‘pirouettes’.”

Over the last decade, the ESA spacecraft has recorded an astonishing three trillion observations. This includes detailed information on the positions, distances, and motions of stars, as well as insights into their compositions and temperatures. Its constant scan of the galaxy has also detailed the orbits of over 150,000 asteroids and discovered a new type of black hole and several exoplanets.

A revolutionary mission

Gaia's data has transformed astrophysics. By accurately pinpointing the positions of stars, Gaia has allowed scientists to measure the Milky Way’s size and shape more precisely than ever before.

Not only has Gaia allowed us to map the Milky Way and learn about its evolution, but it has also enabled astronomers to model how the galaxy might look to an outsider.

“Even basic ideas have been revised, such as the rotation of our galaxy’s central bar, the warp of the disc, the detailed structure of spiral arms, and interstellar dust near the Sun,” says Stefan Payne-Wardenaar of the Haus der Astronomie in Germany.

Since 2016, various researchers have accessed Gaia’s data over 580 million times, and it is the basis of over 13,000 scientific papers. However, just one-third of Gaia’s data has been published so far, and there remain years more information to be released to the scientific community.

Retirement years

On January 15, Gaia made its final starlight observations. But its mission is not quite over. The spacecraft will release two enormous data streams over the coming months before retiring to become a test vehicle.

On March 27, Gaia will leave its current orbit at the second Lagrange point (L2). It will move into an orbit further away from Earth so that it does not interfere with other spacecraft. Until then, scientists will use it to learn more about how technology behaves after a decade in space. 

For a short period, amateur astronomers will be able to see Gaia before its final goodbye. The ESA has created a guide on how to spot the spacecraft.