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The Week in Space and Physics: A Flash of Dark Matter? - The Quantum Cat

2026-09-08T12:31:23.000Z

A Falcon Heavy streaks skyward, lofting the Nancy Grace Roman Space Telescope into the heavens. Credit: NASA/John Kraus.

If the cosmologists are right, dark matter should be everywhere. More than that – it should outweigh the ordinary kind, the kind that makes up all the planets, stars, and galaxies, by a factor of about five to one. It can seem odd, then, that no direct sign of dark matter has ever been seen here on Earth.

Most physicists believe dark matter is some kind of fundamental particle. Yet, it must be one that rarely interacts with the atoms that make up our world. Such things are known. Neutrinos, for example, are ghostly creatures that all but ignore the electromagnetic force and can pass through an entire planet without making themselves known.

Particles of dark matter may take this to an extreme. In theory, they could interact only through gravity, and thus remain aloof and untouched by all other forces. If that’s the case, our hopes of detecting them are slim indeed. Even in theory, it is all but impossible to build a device that could spot such an elusive being on Earth.

If, however, dark matter instead belongs to a category of particle known as WIMPs – weakly interacting massive particles – then it could be found. WIMPs, though still hypothetical, should on occasion hit an atom, and so should sometimes leave a signature in the right kind of detector. In the hope that this is the case, one such experiment, LUX-ZEPLIN, has been running in South Dakota since 2021.

The LUX-ZEPLIN detector. If a WIMP-like particle enters the chamber, there is a small chance it may collide with an atom of xenon. If it does, it will create a flash of light, and this flash is spotted and measured by the photomultiplier tubes. Credit: LUX-ZEPLIN.

Until now, it had found little. But in an announcement last week, project scientists reported that a single unexplained event had taken place in June 2023. It looks, they say, almost exactly as might be expected if an unknown particle had entered the detector, collided with an atom there, and sparked a flash of light.

This is not the first time the experiment has seen something like this. Yet on all previous occasions, later analysis found the events could be explained by things like external disturbances or known particles. This time, researchers say, they have uncovered no such explanation.

Could this be, then, the first sign of dark matter in a laboratory on Earth?

So far, we don’t know. Project scientists are cautious. There could be a mistake in the analysis, they say, and a single event is not enough to claim a discovery with any confidence. Even the one we have looks a little odd. Surprisingly, the particle seems to have carried a lot of energy, seeming to imply that there are more lower-energy collisions we have somehow missed.

Since June 2023, however, the experiment has collected much more data. Analysis of this is ongoing. If that study finds more signs of this unknown particle, then a discovery of something – perhaps dark matter, perhaps something else – may be coming. If not, however, then the long search for the hidden side of the cosmos will have come up empty once again.

Have We Found a Glueball?

Researchers at an experiment in China say they have found signs of a new particle that looks like the long-hypothesised glueball, a particle made entirely of gluons. Though theorists predicted such a thing half a century ago, until now no one had found evidence that they really existed in nature.

As their name hints, gluons are particles that help glue other particles together. They are, in fact, a key part of the strong nuclear force: just as photons carry the electromagnetic force, gluons do the same for this force that binds quarks into protons and neutrons.

Indeed, without gluons, we would not be here at all. Quarks and gluons are essential partners in every atom. Without them, they would have no nuclear structure, and all the things that atoms come together to form could not exist. There would be no stars, no planets, and no people either.

Though similar in function to photons, gluons are more complex. Whereas photons have no electric charge, and so aren’t deflected by electric or magnetic fields, gluons do carry a charge. This charge – known in the language of the strong nuclear force as a colour charge – means that gluons can attract other gluons.

This allows for the possibility of a glueball, a grouping of gluons holding no quarks at all. Though the theory behind this is well established, glueballs are hard to identify in practice, and so clear proof of their existence has yet to emerge.

Mesons contain two quarks, held together by gluons. Baryons - like protons and neutrons - contain three quarks. Glueballs, by contrast, are just gluons with no quarks at all. Image credit: University of Glasgow.

Still, the Chinese research, which is based on years of data collected at a particle collider in Beijing, shows signs of a new particle that matches some predictions of what a glueball should look like. Unfortunately, though, the data is not yet strong enough to be certain.

But if further work does back up the claim of discovery, then the new particle will add to the weight of evidence supporting our modern theories of physics. Studies of the glueball might well help us pin down what uncertainties remain in the Standard Model of Particle Physics.

Next Stop, Mercury

Eight years after it launched, BepiColombo is soon to enter orbit around Mercury.

The mission, a joint project between Europe and Japan, is made up of two spacecraft. They have flown to Mercury together, and have spent most of that voyage attached to the same propulsion system. That system has slowly lowered the pair through the solar system, and last week completed the final manoeuvre needed for them to enter orbit around the innermost planet.

With that job done, the propulsion system – known as the Mercury Transfer Module – separated from the two spacecraft. They will now fly on, still joined, until they reach orbit. But at that point they too will separate, with the European spacecraft – the MPO, or Mercury Planetary Orbiter – moving to a lower altitude to get a closer view of the planet’s surface.

Images of Mercury captured by BepiColombo as it flew past the planet last year. This time, BepiColombo will enter orbit. Credit: ESA/BepiColombo/MTM.

MPO is equipped with eleven different instruments. These will be focused on the surface of Mercury, and should give us one of the most detailed looks yet at the small, hot planet. MESSENGER, the only previous spacecraft to orbit Mercury, revealed a grey, rocky surface pocked by craters and battered by radiation. Despite the heat, pockets of water ice may still be found there, especially in shadowed corners of craters.

The Japanese probe, Mio, will stay in a higher orbit. Its instruments will study the magnetic field of Mercury and look at how the planet interacts with the solar wind streaming off the Sun. Mercury is also known to have a thin atmosphere, and Mio will try to trace the origins of this atmosphere and examine how it changes over time.

BepiColombo will arrive at Mercury on November 21. The two spacecraft will separate in early December, with scientific work starting by April next year.

Roman Launches

NASA’s Nancy Grace Roman Space Telescope lifted off on August 30. The observatory, one of the most powerful ever to be sent into space, will now spend three months voyaging towards a target position one million miles from Earth. In the first week after launch, operators confirmed that both a manoeuvre and the initial commissioning of its instruments had taken place as planned.

Roman is equipped with a mirror similar in size and design to that of Hubble, which means it can take images of comparable quality. Yet its optical system allows for far larger images: in a single exposure, project scientists say, Roman can capture an area of sky one hundred times greater than Hubble can manage.

That makes the telescope well suited for surveys of the cosmos around us. Over its initial five-year mission of exploration, Roman is expected to discover everything from planets around distant stars to asteroids flying silently through our own solar system. The first images, NASA says, should come early next year.

Nancy Grace Roman, as it separated from the Falcon upper stage. Image credit: NASA.

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The Week in Space and Physics: The Magic of an Eclipse - The Quantum Cat

2026-08-26T12:31:19.000Z

The solar eclipse of August 12, seen from Spain.

They say that in 585 BC an eclipse stopped a war. One can almost imagine the scene: the stench of blood and the glint of metal, the churning mud, the cries of rage and desperation. Warfare has never been pretty, yet amid all this the Sun suddenly turned black, a terrible crown of white flames appeared all around it, and the day, shorn of its light, faded into night.

What terror! Even today, when we know the clockwork of the planets so precisely that I can tell you the sky over Trafalgar Square will next be fully eclipsed on May 5, 2600 at 5:52 in the morning, the sight of the black Sun is something our eyes struggle to comprehend. For the Medeans of 585 BC, the event must have seemed a sign of divine wrath, a signal of displeasure from the heavens. Such was the impact, we are told, that they put their weapons and began to speak of peace.

According to legend, Thales of Miletus – the first Greek to be called a philosopher – predicted the eclipse in advance. Whether this is true or not is questionable. Thales, despite his learned nature, almost certainly did not have access to the long records he would have needed to spot patterns in eclipse timings.

Maybe it was a lucky guess then, or maybe the whole thing is a myth. The story does, however, show something important: eclipses are so dramatic and terrible that they seem like the work of an angry god. Yet logic can remove them from this divine perch and turn them into something rational, something constrained by the cold laws of mathematics. Thales’ prediction, whether true or not, marked the beginning of the long trend towards bringing the natural world into order.

Later eclipses had their role to play in science too. It was an eclipse of 1869 that helped reveal the extraordinary nature of the corona, and one in 1919 that gave the first clear proof of Einstein’s theory of relativity. Even today, astronomers go to great lengths to study the events: in 1973 they used a Concorde to track the Moon’s shadow for over an hour, and today we have spacecraft in orbit dedicated to creating artificial eclipses.

Still, despite this long rationalisation, eclipses remain something mysterious. In part this is down to the sheer strangeness of the event: nothing can quite prepare you for the sudden disappearance of the Sun, and for the sight of a black disk wreathed in white flames. Even filled with the facts of modern science, our brains can still refuse to accept what our eyes are seeing.

There is, too, an odd coincidence behind eclipses. Nothing says that the Moon and the Sun should appear roughly the same size in the sky. Our natural satellite could be a bit bigger or smaller, a bit closer or more distant, and we would still be here. Yet eclipses would not: a Moon that appears much bigger than the Sun would simply cover it more often, without revealing the flames of the corona. A smaller Moon would appear as a dark silhouette, much as those of Mars do in their pathetic passages over the Sun.

Indeed, such is the coincidence that Earth is the only planet in the solar system to experience true eclipses from its surface. Among all the worlds in the galaxy, ours may be one of only a handful where such drama is possible. Should alien explorers ever reach Earth, our solar eclipses may well be the thing they find most remarkable.

Martian eclipses are sad affairs, with little of the drama of a total eclipse on Earth. Here one was seen by the Perseverance rover in 2024. Credit: NASA/JPL-Caltech/ASU.

The History of Deimos

Mars has two small moons, Phobos and Deimos. They are not like our Moon. Both are very small: Phobos measures fourteen miles across; Deimos measures only eight. We are not quite sure how they formed. Some think they are captured asteroids; others reckon they were once part of Mars itself, and were blasted off in some massive ancient impact.

Today, Deimos appears as a potato-shaped object, with a large basin dominating its southern hemisphere. The rest of the moon seems to be covered in dust and rock, giving it a dull, subdued appearance. All this might be explained if something big once hit Deimos, carved out a large crater, and then rained debris over its surface.

Two images of Deimos, captured from the Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/University Of Arizona

The problem, however, is that such a large collision should have sent shockwaves rippling through Deimos. Instead of simply blasting a crater, a powerful impact could have shattered the moon. To figure out why this didn’t happen, a team led by Sabina Raducan of the University of Bern recently simulated a hundred different possible impact scenarios.

The one that best fits our observations, she says, is a collision with a rock about three hundred metres across. This would have produced a crater of the right size and left enough debris to cover the rest of the small moon. More evidence comes from Hera, a probe that flew past Deimos last year. The team behind that mission – which includes former Queen guitarist Brian May – saw ancient craters buried under a more recent layer of dust and debris.

Such craters should have been destroyed in a large impact. That they weren’t suggests Deimos is actually not very solid – if it is more like a pile of rubble than a solid body, then any shockwaves from a collision would have quickly died down. The craters would have survived, only to be buried under dust and rock slowly settling after the impact.

Whether this tells us anything about Deimos’ origin is harder to say. Since many asteroids appear to be loose piles of rubble, the findings might seem to strengthen the idea it is one that was captured by Mars. But it could equally be the case that Deimos formed from rubble blasted off the surface of the Red Planet. Whatever the truth, we’ll probably need to get a much closer look at the small moon to figure it out.

Sausages and Krakens

Not all the stars in the Milky Way were born here.

Like all big galaxies, ours grew to its current size through a series of collisions and mergers. Since stars live a long time, some of those that were born in these alien galaxies are still here, moving quietly through the night. In recent years, telescopes like Gaia have started to trace these stars.

Their findings, however, suggest that only one big collision – with the Sagittarius Dwarf Galaxy - has taken place in the past ten billion years. Before that, things seem to have been more chaotic. The best studied merger is one with a galaxy named the ‘Gaia-Enceladus Sausage’, an event that left a lasting imprint on the structure of the Milky Way. Hints of big previous collisions abound, but it has so far been hard to trace these events.

The collision of the Milky Way and the Sagittarius dwarf galaxy. Illustration from ESA.

In a new study, researchers used Hubble to look at clusters of stars orbiting our galaxy. Some of these, they found, formed within the young Milky Way. Others came from the Sausage. But there also seems to be a third set. These clusters, they think, came from an even earlier collision.

They have named the unfortunate galaxy the ‘Low-energy-Kraken-Heracles’, and think that it brought the mass of about five hundred million suns into the Milky Way. Such a merger would have been a highly significant moment in the history of our galaxy – and it is probable that some features of the Milky Way date from that time. Future telescopes, including the upcoming European Plato spacecraft, should give us a better idea of what happened more than ten billion years ago.

No Rescue for Swift

NASA last week abandoned an effort to save the orbiting Swift Observatory.

The plan was to send a spacecraft, named LINK, to grab hold of Swift and then give it a propulsive boost into a higher orbit. All this came together quickly: NASA only awarded a contract for the spacecraft last year, and Katalyst – the company that built it – managed to get it ready for launch in less than twelve months.

But after reaching space, the rescue mission suffered critical problems. Reaction wheels on LINK failed, leaving operators unable to properly control its attitude. Without the ability to accurately point the spacecraft – and therefore to grab Swift - NASA concluded that a rescue was impossible.

This means that Swift will probably re-enter the atmosphere later this year. After more than two decades scanning the sky for gamma-ray bursts, the mission will thus come to an end. That is a shame – the telescope still returns useful data. The failure of the rescue is also unfortunate. Had it succeeded, it could have served as an example of how NASA could soon save Hubble from a similar fate.

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The Nancy Grace Roman Space Telescope - The Quantum Cat

2026-08-23T12:03:05.000Z

The Nancy Grace Roman Space Telescope during tests before launch. Image credit: NASA.

The worlds of astronomy and espionage can seem, well, light-years apart. One deals with the messy realm of human affairs, with seduction and threat, with cunning and guile. The other observes the heavens, divines the movements of the planets, and watches as the stars dance over timescales too long for us even to imagine.

When it comes to space telescopes, however, the two fields suddenly have much in common. The National Reconnaissance Office, or NRO, one of America’s secretive spy agencies, maintains a fleet of advanced telescopes in orbit. They point not up, but down, observing the Earth in great detail.

Hubble, one of the greatest astronomical observatories, was almost certainly based on the KH-11 series of satellites. That relationship was never made explicit, although the similarity in design, shape, and size is a little too obvious to ignore. Sadly, astronomy has not kept up with the spies. The KH-11 is by now on at least its fifth iteration, but we still only have one Hubble.

That may soon change. In 2012, the NRO donated two telescopes to NASA. Both were the result of an effort launched in the 1990s to develop new and improved optics for spy satellites. After that project ran billions of dollars over budget, the effort was abandoned. By the early 2010s, the technology was deemed obsolete for the purposes of espionage, and the NRO thus decided to hand them over to astronomers.

Each carries a mirror 2.4 metres across, similar in size to the one used by Hubble. But thanks to improved technology, they weigh less than a quarter as much, making them far cheaper to put into orbit. The debate about what to do with them quickly settled on one obvious project: WFIRST, an infrared telescope that astronomers had started sketching out a year earlier.

An example of the image quality possible with the NRO’s satellite, as revealed in 2019 via tweet.

Initial designs had called for a mirror 1.3 metres wide. With the new donation, however, engineers could construct something that looked much more like Hubble. The result is a new observatory with Hubble-like resolution, able to take images of about the same quality and sharpness as the old observatory. But thanks to the design of its optical system, it can see much more of the sky, capturing one hundred times more sky than Hubble.

More than a decade after that donation, though, NASA has no clear plan for the other mirror. Various ideas have emerged. Astronomers could use it to study the Earth’s outer atmosphere, or to zoom in on asteroids and other faint objects in the Solar System. They could even send it to Mars, where it could map the planet from orbit and turn its gaze towards the Kuiper Belt. The possibilities are exciting – but the money, sadly, seems short.

The Nancy Grace Roman

After a decade of work, WFIRST – now renamed the Nancy Grace Roman Space Telescope – is almost ready for launch. Engineers completed construction and testing last year. The telescope has since been delivered to the launch site, loaded with fuel, and is scheduled for lift-off on August 30.

The original name of this new observatory was the Wide Field Infrared Survey Telescope. Like the James Webb Space Telescope, it is designed to detect infrared light. That makes it especially useful for studying cool objects like planets and brown dwarfs. But unlike Webb – which is able to peer deep into the cosmos – Roman has a wide field of view.

That means it can observe more of the sky in one go. Astronomers have fitted the telescope with a three-hundred-megapixel camera. This is able to make images as sharp as those of Hubble but with one hundred times the area, thus generating much more data. Whereas Hubble downlinks about twenty gigabytes per day, Roman should send back almost one and a half terabytes.

The main components of the Roman telescope. A 300 megapixel camera forms part of the Wide Field Instrument. A module also allows the telescope to be serviced and refuelled in the future.

For its first five-year mission, astronomers have planned three campaigns for the new observatory. In the first, the ‘High Latitude Wide Area Survey’, Roman will look up out of the disk of our galaxy towards the deeper cosmos (hence the ‘high latitude’ part of the name). This should give the telescope a clear view of millions of galaxies scattered throughout the universe.

The images it takes will add to those of Euclid, another space observatory dedicated to mapping distant galaxies. By looking at how invisible mass is distorting the shapes of these galaxies, the pair will help researchers infer the distribution of dark matter across the universe.

Roman’s second campaign, the ‘High Latitude Time Domain Survey’, will narrow the telescope’s focus to a smaller region of space. Once again, this will lie away from the heart of the galaxy. Roman will return to this region repeatedly, creating a timelapse of how it changes. Astronomers hope to capture the events leading up to supernovae, to watch as neutron stars collide, and to track the final encounters of stars and black holes.

The third campaign - the ‘Galactic Bulge Time Domain Survey’ - will swing the telescope towards the centre of the Milky Way. Once more, it will repeatedly capture images to study how it changes over time. This effort that could reveal a hundred thousand new planets, as well as thousands of neutron stars and stellar-mass black holes.

In this work, Roman will be aided by its coronagraph. This is an instrument designed to precisely block the bright light of a star. With its aid, the observatory can capture the far fainter light coming from planets or rings lying close to those stars. Roman is not capable of spotting Earth-like planets, but it should be able to see worlds the size of Jupiter orbiting far away stars.

Alongside these three big campaigns, Roman will be available for general-purpose astronomy. Whenever something exciting and unexpected happens, Roman will be ready to study it. Hubble, in the past, has captured interstellar comets, peered at stars showing signs of possible engineering projects, and imaged the aftermath of violent explosions. Roman will do much of the same.

Beyond the Stained Glass

“Looking through the atmosphere”, Nancy Grace Roman once wrote, “is like looking through a piece of old stained glass”. The dusty, turbulent layer of air above us blurs the light of the stars. This can be beautiful: the motion of air gives starlight its warm twinkle. But this comes at a cost for astronomy. The twinkling of the stars puts a limit on how well we can know them from the surface of the Earth.

Astronomers have some clever solutions to this problem. They build observatories in places with thin air, like mountaintops, or with cold, stable air, like Antarctica. They put telescopes on aircraft and hot air balloons. They measure disturbances in the atmosphere by using laser beams, and so correct for the distortions introduced by moving air currents.

But the best solution, as Oberth and Spitzer realised early in the twentieth century, is to ascend above the atmosphere. In the 1960s, as astronauts raced to the Moon, NASA calculated that the Saturn V could carry a large mirror into orbit. Once in space, it would be freed of the constraints of Earthly astronomy, and offer the first view of the stars as they really are.

Unfortunately, things turned out to be more complicated than simply getting it off the ground. Technology had to advance, money had to be found, and politicians had to be persuaded. Throughout the 1960s and 70s, Nancy Roman pushed NASA to take the idea seriously, and encouraged Congress to fund the project. Eventually those efforts bore fruit: Hubble, the first large space telescope, was completed in the 1980s and launched in 1990.

A simulation of how Roman’s images of the Andromeda galaxy might look. All this can be imaged in a single exposure - although gaps in the detector mean it does not appear as a single continuous image. Credit: NASA's Goddard Space Flight Center.

Since then, it has been joined by half a dozen other big space telescopes. Gaia mapped the stars; Euclid is studying the galaxies; Chandra searches for X-rays coming from violent events. Webb, with its six-and-a-half-metre mirror, is perhaps the greatest of them all. It has peered deeper into the cosmos than ever before and revealed we know far less than we thought we did about the early epoch of the universe.

The Nancy Grace Roman Space Telescope, named for the woman who helped make the idea of space observatories a reality, is the latest to join this club. Our growing capabilities, including a new generation of giant observatories on the ground, allow these telescopes to work together, instead of in isolation.

Webb, like Roman, is an infrared observatory. But where it has a narrow and deep view, Roman can go wide. The two can thus work together, just as Euclid – an optical observatory – will work with Roman to map the shapes of galaxies and trace the presence of dark matter. Even the ageing Hubble – in some ways a sister craft to Roman – can see light that Roman cannot, and can thus produce a more complete view.

Roman’s work will begin at the end of August. After launch, the telescope will slowly make its way out to a point one million miles from Earth. During its first three months in space, operators and scientists will commission the telescope, calibrate its instruments, and ready it for the serious work of astronomy. And then, far above the stained glass of our atmosphere, Nancy Grace Roman will see the stars as they really are.

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The Week in Space and Physics: The Wandering Black Holes - The Quantum Cat

2026-08-11T12:31:16.000Z

The surface of the Sun. Credit: NSF, NSO, AURA, MPS, Inouye Tel.

It sounds like the stuff of nightmares. A rogue black hole emerges out of nowhere, swallows the planets one by one, and then stretches the Sun out into a long stream of glowing dust. We – if we even make it beyond the first moments of such a disaster - have little chance of survival.

Nightmarish though it appears, this may well have been the fate of a recently discovered star in a far distant galaxy. It was only spotted in November last year, when a brilliant flash of light suddenly lit up the galaxy. Over the following months it faded – but when astronomers traced back the event, the conclusion that best fitted was a deadly encounter with a wandering supermassive black hole.

These beasts normally lurk in the centres of galaxies. There they are obvious: they are surrounded by clouds of dust and gas swirling around at tremendous speed and emitting bursts of radiation. In our own galaxy, this radiation signature was first detected in 1933, when pioneers of the radio picked up a strong signal coming from the heart of the Milky Way.

Sometimes, however, they leave their natural homes and begin to wander. This is most likely to happen when galaxies collide. In many cases, the black holes of the two merging galaxies end up spiralling around one another, gradually drawing closer and closer until they combine into a single heavyweight that remains at the centre of the newly enlarged galaxy.

At times, however, the situation can become more complex. Should a third black hole get involved – perhaps because one of the colliding galaxies already hosts a spiralling pair – then one of the black holes can be ejected. Or, perhaps, a small galaxy might encounter a far larger one. Its stars get torn off and stretched out into a long stream. Its black hole is left alone, and then begins a long fall through the larger galaxy.

Either way, the result is a wandering supermassive black hole. Such objects are hard to detect. Alone, they barely emit any radiation. They gather little in the way of dust and gas, and it is only when they encounter and destroy an unfortunate star that they betray their presence. Such catastrophes are called tidal disruption events.

Over the past few years we have seen several possible candidate events. All occurred in other galaxies, and each looked like a sudden burst of radiation created as a star was violently ripped apart. The event of November 2025 – which took place more than thirty thousand light years from the centre of its galaxy – is notable for just how far this black hole seems to have wandered. For reference, we lie about twenty-five thousand light years from the centre of our galaxy.

The dynamics and behaviour of these wandering black holes are still poorly understood. We do not know, for example, if black holes are more likely to be heading outwards, or falling inwards. Fortunately, the new Vera Rubin Observatory is poised to change things.

It has been designed to look for sudden flashes of light in the night sky. Some of these will be stars dying natural deaths. Others will be signatures of a violent encounter between a star and a wandering black hole. Astronomers hope this data will reveal hundreds of such cases – and thus show more about how they behave and how they move.

Betelgeuse and Its Companion

Speculation has been growing for some time that Betelgeuse is not alone.

The star is one of the brightest in the night sky, and is the closest one likely to erupt in a supernova in the near future. Nobody knows exactly when this dramatic event will occur, but it should take place within the next hundred thousand years. The day that it does finally explode, observers here on Earth will see one of the most brilliant events to ever appear in the night skies.

For some time, observations have shown that Betelgeuse fluctuates in brightness. These changes can be extreme – at times it is among the very brightest of stars, at others it drops almost entirely out of the top twenty. Part of this is probably caused by its imminent demise: a sudden darkening a few years ago was triggered by an outburst of dust from the star.

But astronomers also know that Betelgeuse follows a regular cycle of brightening and darkening. This pattern has made some wonder if it has a hidden companion, a fainter and smaller star that is locked in orbit around the dying giant.

In 2024, two separate studies modelled the orbit of this possible star and predicted it would be furthest from Betelgeuse in December of that year. Since that would make it easier to see, a team led by Miguel Montargès of the Paris Observatory decided to use the Very Large Telescope (VLT) in Chile to try to find it.

The companion star, marked by the crosshairs. The circle shows the position of Betelgeuse, though to take this image its light had to be removed. Credit: ESO/M. Montargès et al.

They now say they found something. The images they took quite clearly show a star close to Betelgeuse, in roughly the predicted place. Montargès says it is “more massive than predicted”, which had the fortunate effect of making it brighter and easier to see than expected.

To confirm the discovery, astronomers will want to see the star moving. By next year it should have moved to the other side of Betelgeuse. If it has, new images should show this, and that would finally confirm that Betelgeuse is not alone.

The Surface of the Sun

A telescope in Hawaii captured the highest-resolution image of the Sun’s surface ever made (shown as the cover image above).

The picture shows the photosphere of our star, that is, the outer shell from which the Sun’s light shines. This layer often has a granular, boiling appearance, caused by bubbles of hot plasma rising up from below before cooling and falling away. At times, it can be blemished by sunspots, each of which reveals an area temporarily cooler and darker than the rest of the photosphere.

The new image focuses on a region of the Sun close to a sunspot. It shows the surface covered in moving bands and vortices, structures that astronomers think are signs of Kelvin-Helmholtz instabilities. These are created when a velocity shear is present in a moving fluid, for example, when fast- and slow-moving fluids come into contact.

Astronomers had theorised that these instabilities should appear on the Sun’s surface. But this image is the first confirmation they actually exist. They are thought to play an important role in moving magnetic energy around the Sun’s surface, and in transferring heat outwards into our star’s outer atmosphere.

Solar Eclipse

A total eclipse of the Sun will take place on August 12.

The Moon’s shadow will race across the Arctic and Atlantic Oceans, making landfall over Greenland, Iceland, and the Iberian Peninsula. In mainland Spain, it will be the first total eclipse seen in more than a century – the last took place in 1905, though one was seen from the Canary Islands in 1959. Yet it will also be the first of a run of three Spanish solar eclipses that will occur in 2026, 2027, and 2028.

Credit: ESA.

The path and timing of the eclipse offers a few remarkable possibilities. During its early hours over the Arctic, the sudden darkness could allow the aurora to become visible in the middle of the day. As it reaches Spain, the eclipse will accompany the setting of the Sun, giving observers a rare view of a crescent Sun disappearing over the horizon. Those who stick around have a chance to see the Perseid meteor shower, expected to peak during the night of August 12.

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Reflections on Placing Mirrors in Space - The Quantum Cat

2026-08-04T12:28:59.000Z

Znamya-2, the first and so far only mirror to fly in space and reflect sunlight back to Earth.

In the world of The Lord of the Rings, the morning star bore the name of Eärendil. Song and legend told that he had been a great mariner, that he was born half-man, half-elf, and that after he had ventured into the lands of the godlike Valar, they had sent him and his ship to eternally sail the heavens.

The tale has similarities to ancient myths about the stars. At times the gods sought to protect: the Pleiades, it is often told, was once a group of seven girls fleeing mortal peril. At other times, they punished: Orion, the Greeks said, was a hunter condemned for his arrogance and placed into the heavens only after he was killed.

According to Tolkien, Eärendil should have been slain for daring to set foot on the forbidden lands of the Valar. Yet as he had acted not for himself, but on behalf of both men and elves, they chose to spare him. Instead, they sent him and his ship into the great ocean of the sky. On his forehead was placed one of the Silmarils, a brilliant jewel shining with the magical light of Valinor, and it was said he would always return to our skies to mark the rising or the setting of the Sun.

The legend was inspired by a collection of Old English poetry, among which there was a reference to Earendel, the brightest of angels. In his letters, Tolkien argued that Earendel, the brilliant herald of the rising Sun, was a clear reference to the morning star1. Today we call that star Venus; in Old England they may have called it Earendel; in Middle-earth they knew it as Eärendil.

A design for a giant orbiting space mirror, from a 1982 NASA technical study on their feasibility.

Soon, a new Eärendil may appear in our skies. This time it will not be the morning star, but instead the herald of something far more terrible. Eärendil-1, a satellite now being built by an American company called Reflect Orbital, is designed to outshine Venus, to reflect the light of the Sun onto the Earth below, and to briefly turn night into day.

If it works, and if Reflect can raise the money, the satellite will be followed by thousands more. By 2035, Reflect Orbital projects they will have fifty thousand satellites in orbit, and together they will have the power to banish darkness over any corner of the planet and at any hour of the clock.

Their website spells this mission out in noble terms. Putting an end to the night will help humanity generate energy from sunlight, aid rescue workers struggling with poor lighting, and reduce the need for artificial street-lighting.

They will achieve all this by using gigantic mirrors. Eärendil-1 will carry a folded-up reflective sheet. Once the spacecraft reaches orbit, this sheet will unfurl like a sail, creating a mirror measuring eighteen metres (sixty feet) across. From the Earth’s surface, the spacecraft will appear like a bright and fast-moving star, reflecting enough sunlight to cast shadows on the ground.

Reflect say they can steer the Sun’s light to a circle measuring five kilometres, or three miles, across. Inside this circle the satellite will appear as a bright star; outside it will fade into obscurity. But because the satellite is moving fast, it will be able to illuminate the area for no more than a few minutes. To extend the coverage, Reflect will need more satellites – and this is the reason why they want to launch fifty thousand of them over the next decade.

In Russian, the concept for Znamya. The space station Mir is shown in the upper left. The mirror, deployed from the station, reflects the Sun’s rays onto the night side of the Earth.

It is said that Archimedes, the great engineer of Syracuse, once arranged a series of mirrors to reflect and focus the Sun’s rays onto the ships of an invading Roman navy. The goal was to set them ablaze, halt the invasion, and save the city. That may have worked for a while, but eventually the Romans decided to approach the city at night, opened its gates with the help of a traitor, and put Archimedes to death after the citadel fell.

Two millennia later, as the German scientist Hermann Oberth contemplated putting mirrors in orbit, military matters were still at the top of everyone’s minds. By focusing the Sun’s rays, Oberth wrote, a ray of heat could be directed onto enemy cities. The idea was absurd, naturally, but after the Second World War, claims emerged that both Germany and Japan had been secretly working on ways to make it a reality.

Oberth also saw civilian applications in the idea. He thought an orbiting mirror might open up shipping routes during the long Arctic nights, or be used to alter the weather. Others imagined using them to cool Venus, or to make Mars habitable. In the 1980s, Vladimir Syromyatnikov, a Soviet scientist, proposed using a mirror to help Russians work in the frozen northern winters2.

As with Eärendil-1, the benefits seemed enormous. Syromyatnikov thought space mirrors could extend the Russian agricultural season and perhaps be used to carve channels through polar ice sheets. In 1992, a prototype mirror – Znamya-2 – was sent to the Mir space station. In February 1993 it was deployed, the mirror unfurled, and a beam of light swept over Europe and Russia.

The night was unfortunately cloudy. But those who saw the beam reported it briefly shining as bright as the full moon. From space, cosmonauts reported seeing a faint circle of light race over the Earth’s surface at tremendous speed. The test was a clear success, but a short-lived one: within a few hours the mirror had fallen back to Earth and burned in the atmosphere.

A second effort followed in 1999. Znamya-2.5 held a far bigger mirror and was supposed to shine ten times brighter than the full moon. But soon after it was deployed, it snagged on an antenna. Efforts to free it failed, leaving the mirror crumpled and ripped. With the situation beyond salvation, Znamya-2.5 was instead jettisoned and left to burn up as it fell.

Satellites are already making astronomy harder, as this timelapse showing one hour of satellite trails over Chile shows. Credit: F. Kamphues, ESO/M. Kornmesser

The partial success of Znamya proves the feasibility of Eärendil-1. Of course, operators can always run into unexpected problems: new spacecraft often fail, unfurling a giant mirror – as Znamya-2.5 discovered – is not a straightforward task, and no one has ever steered an orbiting mirror before. But the basic concept is, at least, sound.

Yet, just because we can do something doesn’t mean we should. The launch of Znamya-2.5 sparked outrage from astronomers. The bright lights cast by orbiting mirrors could render their work impossible, they complained. Messing with the night could cause unexpected problems, others warned, and would impact everything from animal life to human psychology.

The same concerns have been raised again. A recent study by the European Southern Observatory found that Reflect’s plans would put an end to ground-based astronomy. Space observatories are powerful, but expensive and far from able to replace what we do from the Earth’s surface. Should Reflect succeed, it would kill astronomy as we know it.

Neither does the economic case look convincing. Reflect Orbital pins much on its ability to let solar power farms run into the night. Yet the amount of solar energy they can reflect onto the Earth is small, and the mirrors cannot focus well enough to direct all that power onto solar panels. Most of what they will deliver will be lost; whatever does get through is unlikely to be enough to bother collecting 3.

That makes it unlikely Reflect will ever earn enough in the way of profits to build, launch, and operate their full constellation. But Eärendil-1 is still likely to fly. The spacecraft has been authorised by the American government. A launch on a SpaceX rocket could come in the next few months.

“All that is gold does not glitter”, Tolkien wrote. Eärendil-1 may prove the truth of this. The technology can work. The economics, and the morality, are far less likely to shine. After all, who really wants a giant flash light shining upon their house from the heavens?

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In the poem, Earendal symbolises John the Baptist. Just as the morning star heralds the coming dawn, so John heralded the coming of Christ.

There was an attempt to mark the 500th anniversary of Columbus’ trans-Atlantic voyage by sending a regatta of solar sails to Mars. When the effort failed, the engineers behind the Soviet entry switched their efforts towards reflecting sunlight instead of sailing to the planets.

Estimates suggest you would need thousands of mirrors working together to reflect enough sunlight for solar panels to work well. The laws of orbital mechanics also dictate that the mirrors will be moving fast and need to constantly repoint to steer the reflections correctly.

The Week in Space and Physics: Finally, an Exomoon? - The Quantum Cat

2026-07-31T14:02:56.000Z

An artists impression of the recently discovered exomoon and its brown dwarf. Credit: ESO/M. Kornmesser.

As a reminder, last weeks article So Simple a Thing as a Star is available for download in PDF and EPUB formats. You can buy access here.

Exomoons are strange beasts. They shouldn’t be, of course. The galaxy is full of planets, and those planets should have moons just like those found in our solar system. There are probably billions of these perfectly normal moons (‘exomoons’) scattered across the sky.

Unfortunately, they are hard to spot. Normal moons are small, faint, and all but invisible across the vast spans of interstellar space. This means that the handful of possible exomoons that we may have seen are weird creatures. Almost all contenders are gigantic, more like twin planets than true moons in orbit around a larger world.

None of these possible moons have been confirmed. Most claims of discovery rely on faint pieces of evidence, and could be explained in other ways. But a new study, released by the European Southern Observatory, claims to have found plausible evidence of something that could be called an exomoon in a star system almost seventy light-years distant.

Like the others, it is an odd object. It is found in a system called CD-35 2722. This system is dominated by a small star, one about half the mass of the Sun. Around this star orbits a brown dwarf, an object that is too small to shine like a star, but also too big to be considered a normal planet. In some ways, these dwarfs can appear as failed stars – above all, they lack the mass to sustain nuclear fusion.

The leader of the study, Kevin Hoy, discovered another object orbiting this brown dwarf. It seems to be quite big; indeed, Hoy says it is at least as big as Jupiter. That makes it far bigger than anything we could normally consider a moon. Yet this system makes these definitions hard. The ‘moon’ is clearly in orbit around a bigger ‘world’, itself in orbit around a star.

In our solar system, “defining things like moons is simple”, says Alice Zurlo, a collaborator on the project, but in this system things are “much more complicated to describe”. Whether we are willing to call it a moon or not, this strange system at least seems to be unique among those we have observed.

Future exomoon discoveries are likely to be just as bizarre. Our telescopes are only capable of picking out the very largest of them. The next one we discover could be the size of Neptune or Saturn, and could be spotted in orbit around a world bigger than Jupiter. Just as in the strange case of CD-35 2722, whether we can call such gigantic companions true moons is up for debate.

In many ways, the paucity of true exomoons is a shame. The moons of our solar system – Europa, Titan, and Enceladus among them – are some of the most dynamic and exciting places we know beyond Earth. If we are going to find life in the cosmos, an exomoon would not be a bad place to look.

A Return to Tranquility Base?

Tranquility Base lies almost exactly on the equator of the Moon. Mission planners chose the site, the famous landing place of Apollo 11, as an easy spot to leave the first footprints beyond Earth. Its equatorial site made it easy to reach, and its terrain was free of risky cliffs or deep craters.

The other Apollo landings targeted sites scattered across the near side of the Moon. Yet all remained close to the equator. No spacecraft – not even a robotic one – targeted the lunar poles until 1998, when the Lunar Prospector was deliberately crashed near the Moon’s South Pole.

Since then, however, interest in the southern pole has been rising. In 2009, LCROSS confirmed the presence of water ice near the pole, though it was not until 2023 that the first spacecraft – Chandrayaan-3 – successfully landed in the region.

Both America and China now believe the lunar south pole is the key to building a long-term base. Though the region is challenging – it is rocky, strewn with craters, and awkwardly placed for communications – it does hold plenty of water. The two nations are, therefore, planning for future crewed visits to the southern pole.

In July, however, astronaut Victor Glover called for a rethink. He was one of the four who flew on Artemis II, and thus part of the first crew to get anywhere close to the Moon in half a century. He believes the return to the Moon should start with a flight to the equator. It is easier to reach, he says, safer for landing, and has much better lighting conditions.

Since NASA is trying to accelerate plans to land on the surface, the equator would seem like a better initial option. If America’s politicians want to see a flag and footprint on the Moon as soon as possible, they will have better odds of success if they choose an easy landing site. The poles may be better for a sustained presence, but they are far harder, and far more likely to cause delays.

Technosignatures in White Dwarfs

In the far distant future, the Sun will swell up into a red giant, consume the inner planets, and then gradually fade into a white dwarf. The remnants of our world, along with any technology we might have left behind, will eventually fall upon this dwarf star. When they do, they will create a faint but long-lasting signature of our presence here.

Studies of white dwarfs elsewhere in the galaxy have found many signs of the worlds that once orbited them. These are called ‘polluted’ white dwarfs, and they often have traces of metals like silicon in their atmospheres, as well as elements like carbon that came from destroyed planets.

This, a recent paper in The Astrophysical Journal pointed out, could give us a way to hunt for the signs of ancient alien civilizations. If such a civilization had long ago emerged around a Sun-like star, and if that star had eventually died and consumed their homeworld, traces of their technology may still be visible in the resulting white dwarf.

To test their idea, they examined almost seven hundred white dwarfs, looking for any deviations from what might be naturally expected. They found nothing significant. A few stars, however, seem worthy of further study: we cannot yet say if they were once home to aliens, but they do at least show signs of something unexpected going on.

SpaceX, Starship, and Stock Prices

SpaceX launched Starship for the thirteenth time. After a false start – the first launch attempt ended with a dramatic last-second abort – the second attempt passed smoothly.

The initial abort was caused by engine problems. Six of the rocket’s thirty-three Raptor engines had failed to start properly, and two, SpaceX said, had to be replaced. That led to a delay of a week, after which SpaceX delayed another day due to weather. But when the count did again reach zero, Starship lifted smoothly off the pad.

Overall, the test flight went well. Starship deployed some test satellites and demonstrated the relighting of an engine in space. That may pave the way for Starship’s first orbital flight within a few months – finally allowing SpaceX to move beyond the suborbital trajectory every test flight has followed so far.

The success, however, had little impact on SpaceX’s ailing stock price. After joining the stock market on June 12th, the company briefly reached a value close to three trillion dollars. Today, investors value it at less than half that price.

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The Solar Probe: So Simple a Thing As a Star - The Quantum Cat

2026-07-24T12:31:15.000Z

The view from inside the solar corona. Here the Parker Solar Probe captures the solar wind streaming out from the Sun. Credit: NASA/Johns Hopkins APL/Naval Research Lab.

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It is reasonable to hope that in a not too distant future we shall be competent to understand so simple a thing as a star.

Arthur Eddington, 1920

Usually, you have to be dead before anyone will even consider naming a spacecraft after you.

Einstein had to wait twenty years for the honour. Hubble had been buried four decades before he got his famous telescope. In Europe things can be far worse: Euclid was in the ground for twenty-three centuries before he got anything, and Plato – dead in 347 BC – will only get one next year.

But Eugene Parker somehow broke all the rules. On August 12, 2018, the man – then still very much alive – stood and watched as the Parker Solar Probe soared into the heavens. Perhaps it seemed normal to him. He was, after all, no stranger to having things named in his honour: Parker has an Equation, a Model, a Limit, and an Instability. The Parker Spiral describes the way the Sun’s magnetic field twists in space; the Parker Theorem talks about how magnetic fields move through plasmas.

All this – the probe, the equations, the instabilities – is a tribute to a man who tried harder than almost anyone else to understand the Sun. He arrived on the scene in the 1950s, a time when some of the big questions about our star – notably what it was made of, and how it burned – had been solved. But science still viewed the Sun as a static object, one with limited influence on the rest of the Solar System.

Parker initially turned his attention to the solar corona, the mysterious and very hot layer surrounding the Sun. This region, he realised, had to be unstable. His calculations showed that a stream of particles must be constantly blowing off it, forming a fluctuating breeze he dubbed the solar wind. The idea was instantly ridiculed – a reviewer of his paper called it “nonsense” and suggested Parker spend more time in the library before trying again.

But Parker was right. In 1959, the Soviet probe Luna 2 detected particles streaming off the Sun. Three years later, Mariner 2 confirmed the discovery as it flew towards Venus. The solar wind was very real, and the Sun was shown to be far more dynamic and influential than anyone, bar Parker, had dared to believe.

In the years after, he made other important discoveries. He looked at how the Sun’s magnetic field behaved, studied its mysteriously hot corona, and pondered the question of magnetic monopoles. When he died in 2022, he was hailed as the father of heliophysics, a man who had written his name in the stars.

Yet, and despite all his work, we still struggle to understand the Sun. It is, as the physicist Arthur Eddington pointed out early in the twentieth century, very much an average star. It is of an unremarkable size, an unremarkable age, and appears little different to countless others scattered across the galaxy. It should be easy to understand.

But it has proven surprisingly complex. The mystery of how and why the corona is so hot – at times it can reach temperatures of ten million degrees, far higher than those of the surface of the Sun – remains unsolved. So too do questions about the origins of the solar wind, and the reasons why enormous flares occasionally burst out from its surface.

The only sensible solution, NASA realised, was to try something utterly insane. To properly grasp the workings of our star, we needed to fly as close to it as possible. The goal of the Solar Probe was to do exactly this: to approach the Sun, to penetrate its outer layers, and to plunge through the soaring heat of the corona itself.

“Wow!”, Eugene Parker said, as he watched his namesake lift off the launch pad and begin this perilous and unforgiving voyage. “Here we go!”.

The Week in Space and Physics: The End of The Night Sky - The Quantum Cat

2026-07-14T12:31:32.000Z

One hour of satellite trails over the Atacama Desert. Image credit: F. Kamphues, ESO/M. Kornmesser.

Until the moment Sputnik launched in 1957, the night sky remained a wilderness untouched by the hand of Man. People who looked up, and who did so far enough away from the glare of city lights, could see pretty much the same sky as every other human had since the dawn of consciousness.

Since that day, however, things have changed. Sputnik itself was not that bright, but its rocket booster was, and for a few days it shone as bright as a first magnitude star. Today there are tens of thousands of artificial objects orbiting our world, and on any clear night the impact of our work can clearly be seen.

Some hail the progress this has brought. The majority of active satellites now in orbit belong to the Starlink constellation, a massive piece of infrastructure that provides Internet connections across the world, as well as aiding the espionage and military capabilities of the United States. But it has come at a price.

The night sky is no longer a pristine wilderness. Astronomers have suffered, as satellites leave bright trails across their images. Debris, in the form of abandoned satellites and rockets, is gradually building up in orbit. The risks of a collision, or of parts of a falling satellite hitting and killing someone, are rising.

This loss looks certain to continue in the coming years. More Starlink satellites will be launched, especially if SpaceX masters their Starship rocket. Musk has said he wants to launch a million data centres into orbit to power AI. Amazon has started building a huge constellation of their own. China is doing the same, and many others have announced plans.

One of the brightest objects in the sky is now not a planet or a star, but BlueWalker 3, a satellite aiming to provide cellular phone service from space. Reflect Orbital, an American startup, hopes to soon deploy gigantic mirrors in orbit. If they succeed in this rather nonsensical idea, they will create objects that shine as bright as the full Moon.

All this, the European Southern Observatory recently warned, will mean the end of the night sky. Instead of a heavens full of stars and wonder, we will see only a sky shaped by our own hands. In the place of planets, we will see satellites beaming data and turning night into day.

For astronomers, the prospect is frightening. Major astronomical projects, including the Vera Rubin’s ten-year survey and the European Extremely Large Telescope, may be for naught. If the sky holds more than about one hundred thousand satellites, ESO calculates, then astronomy as we know it will become impossible.

It is troubling that much of this change is coming about without proper discussion. The American government has recently approved the launch of Reflect Orbital’s bright satellites – a decision that will be felt by people across the planet, not just in America. They did not consider the impact such giant mirrors will have on the world, nor accept responsibility for the consequences of their actions on the night sky.

The Oldest Impact Crater On Earth

Some of the oldest rocks on Earth lie in the Pilbara region of Western Australia. It is here that we have found the earliest signs of life on our planet, in the form of mineral deposits and other structures probably created by organisms living more than three billion years ago.

The extreme age of this region makes it a good place to look for evidence about the early Earth. One debate surrounds the origin of the continents: many geologists think they were created by immense plumes of molten rock and heat welling up from the interior of the planet. But a team led by Tim Johnson at Curtin University thinks the energy to form them instead came from massive asteroid strikes.

To find evidence to support this idea, they headed to Pilbara in search of ancient impact craters. They found one in May 2021, in a region called North Pole Dome. There is no actual crater there, at least not any more, but they did find signs that the local rocks had experienced an impact shock. In part, this evidence came in the form of geological structures called shatter cones.

They concluded the impact had happened in the distant past, probably more than three billion years ago. But an alternative study, led by a group from Harvard, later reached a different conclusion. They agreed there had been an impact, but thought it had happened much more recently. The asteroid responsible, they found, could have struck the Earth ‘just’ four hundred million years ago.

Now, the Australian team has hit back. They carried out a more detailed analysis of the rocks at the site of the crater, and examined the crystals within them. Some showed an age of 3.4 billion years, and were probably formed along with the rocks. But others showed signs of having experienced a sudden shock, like an impact, and these were dated to about three billion years of age.

Alongside this, they found another mineral, apatite, that forms when heat drives water through fractured rock. As with the shocked crystals, this was dated to an age of about three billion years. Together, the two pieces of evidence suggest we really are looking at the oldest known impact crater on Earth.

Euclid’s Ancient Quasars

The European Space Agency announced the discovery of the earliest known quasars in the universe. They were found by the Euclid Space Telescope, an observatory dedicated to the study of distant galaxies and to the hunt for dark matter and dark energy.

Quasars are, in essence, extremely active galaxies. Their inner black holes are consuming vast amounts of gas and dust and other material, and this creates a furious disc of material swirling around their centres. The result is a hot and bright galactic core, one visible across extraordinary distances.

Indeed, many quasars are far away and are visible as they were billions of years ago. But spotting the oldest quasars has so far been challenging. They are distant, which makes them appear faint, and they can look more like stars than galaxies.

Some of the quasars spotted by Euclid. Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by the Euclid Science Ground Segment and Antoine Basset (CNES)

The Euclid Space Telescope, however, spotted thirty-one of the oldest quasars known. Some were formed in the first billion years after the Big Bang. They seem to be dusty objects, filled with stars forming at a rapid pace.

It is possible the James Webb Space Telescope has seen even earlier quasars, or perhaps objects that eventually evolve into quasars. Since it launched, Webb has spotted dozens of ‘little red dots’ in the early universe. Astronomers are still divided about what they are, but one theory holds that these are primitive galaxies with active central black holes.

If so, the work of the two telescopes may be helping to close a gap in our understanding of how quasars came to be. Many questions, of course, still remain. Astronomers have plenty to learn from these new observations of the early years of the cosmos.

The Greatest Survey Begins

The astonishing landscapes around the Vera Rubin Observatory. NOIRLab/NSF/AURA/C. Corco

The Vera Rubin Observatory began an ambitious ten-year project to survey the night sky. The Legacy Survey of Space and Time, or LSST, aims to create a time-lapse of the heavens, showing how celestial objects change over both long and short time periods.

Vera Rubin is equipped with the world’s largest camera. It weighs three metric tons and can capture 3200 megapixels. All that power will be dedicated to the survey, and it should help the observatory spot countless objects that have so far been missed. The observatory, astronomers hope, will discover millions of asteroids and comets, search for a possible ninth planet, and hunt for traces of dark matter and dark energy.

Construction work on Rubin, built on top of a mountain in central Chile, came to an end in November last year. Since then, operators have been conducting engineering tests and optimising the quality and performance of the telescope and its instruments. They have now decided that both are good enough to start the real scientific work.

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Why Is the Earth Coated in the Dust of a Supernova? - The Quantum Cat

2026-07-09T12:31:43.000Z

The shockwave created by the enormous speed of Zeta Ophiuchi. This star may have been cast out by the same supernova that spread ash across our world. Image credit: NASA/JPL-Caltech.

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Deep under the waves of the Pacific Ocean lie the ashes of a supernova. They exist in the form of rare isotopes of iron and plutonium, each preserved in layers of sediment laid down over long millennia. Such isotopes are not made on Earth. Instead, they can only have been forged by a giant star, and cast into space by the terrible force of its demise.

No one knows the precise shape of events. One theory holds that a massive star exploded nearby, and sent debris raining down upon our planet in a spectacular aftermath. Another argues that the dying star was more distant, the ash collected first into clouds, and only fell upon us as the Earth happened to later pass through.

However it arrived, the ash seems to be everywhere. Similar samples have been found clinging to rocks on the Moon, frozen in layers of ice laid down at the poles, and buried in sediments at the bottom of every ocean we’ve examined. All this material is indisputably of cosmic origin, and could only have been scattered by some catastrophic event.

The obvious cause would be a nearby supernova. Since the ashes seem to have arrived in two clear waves – one two million years ago, the other seven million – some think they hint at the explosions of two giant stars close to our planet. Adding support to this idea is the presence of a vast bubble stretching all around us in space, a region recently swept clear by a powerful shock wave.

At first, the blame for all this fell on Geminga, an energetic and fast-moving neutron star about eight hundred light-years away. It is, quite clearly, the remnant of a big star that exploded. But the timings don’t quite add up: its supernova probably took place about three hundred thousand years ago. It could not have made the ash we found, nor could it have been powerful enough to blow a bubble as big as the one we now see.

Instead, today’s astronomers think about a dozen giant stars have exploded around us in the past fifteen million years. Each helped sculpt the bubble, and each has scattered debris into the space it occupies. Some of these stars might have exploded close to Earth: if they did, they may well have strewn their dust across our world and its moon.

Yet questions remain. It is far from certain how this ash made its way to our planet, or how close these giant stars were to us when they died. A supernova within one or two hundred light years of Earth would have been an extraordinary event. Could one really have blazed in the sky two million years ago, showering us with its debris just as our distant ancestors were beginning to shape stones into tools?

The Slow Rain of Ash

About four hundred light-years from us lies a group of bright blue stars known as the Scorpius-Centaurus Association. These are young stars, each born in the last fifteen million years. Many of those we can see are massive stars that burn bright and die young. When we search for blame for the recent violence, Scorpius-Centaurus seems an obvious place to start.

Studies have indeed found signs of recent supernovae there. One possibly erupted two million years ago, an event that created a fast-spinning pulsar and sent the star Zeta Ophiuchi careening off into space. It might have been close enough to shower us with ash, although we are uncertain precisely where this giant star lay relative to us at the time.

This and another so far untraced event could have been responsible for the two waves of debris we see in the sediment record. But not everyone is so sure. A supernova should create a relatively short pulse of ash, and would need to be extremely close by to produce the amount seen. Yet the sediments show a longer wave than this. Neither does the timing seem to match any known mass extinction of life that would accompany such a nearby and violent event.

Instead, as a paper by Merav Opher, Avi Loeb, and J.E.G. Peek pointed out in 2024, a series of past supernovae would have scattered debris across our region of space. Over time, all this ash and dust would have settled into clouds, and these would have remained spread across the bubble otherwise swept clear by the supernova shock waves.

Every now and then, they say, the solar system passes through one of these clouds. Roughly two million years ago, we could have encountered a particularly dense ribbon of dust. If so, this would have pushed the Sun’s magnetic shield inwards, and allowed a heavy rain of ash and dust to fall upon our world for tens of thousands of years.

In this case, the supernova would not have been especially close to us. Indeed, the star could have exploded at a distance of a few hundred light-years – which is still close, but hardly dangerously so. As long as we encountered the debris cloud it left behind within a few million years, that long-ago event could still have left an imprint on our world.

Pieces of the Sky

In his book Wind, Sand, and Stars, Antoine de Saint-Exupéry remarks on the sight of black meteorites scattered across the sands of the Sahara. There is, he notes, a long, slow rain of these rocks upon the Earth. They remind us that our planet is not alone, not adrift in an empty universe. From time to time, pieces of the heavens fall upon us.

Many of these pieces are subtler and harder to spot than meteorites. The behaviour of the Sun influences the atmosphere: when a strong solar flare hits, it creates isotopes that are picked up and stored by trees. Millennia later, we can find the evidence of these ancient flares marked in their tree rings.

Cosmic dust is another of these quiet hints of a wider universe. It falls slowly on our world. Even today, supernova ash is still coming, but it is doing so at the imperceptible rate of less than a gram a year across the entire globe. To find its signature, scientists must look for the ash atom by atom, teasing it out from records laid down over extraordinary lengths of time.

Recent examinations of polar ice have spotted a subtle shift in this slow fall of dust. The rain is quietly getting heavier. This increase, they say, could mark a change in our interstellar environment; a transition from a void to a cloud, or from one cloud to another. Today we appear to be well inside one such cloud – indeed, we seem to be getting closer to its edge than to its centre.

Researchers have not yet dated precisely when we entered this cloud. Based on what we know, it was probably between ten and forty thousand years ago. All of human history, in other words, from the dawn of agriculture to the awakening of artificial minds, has taken place inside this single, small cloud. Sometime in the next few thousand years, if we last that long, we will move beyond it.

The Sun’s journey through space has been far greater than that. To our short lives, our short civilisation, the stars are almost static. Yet they are not. The ashes at the bottom of the Pacific Ocean tell us something about where we have been. But they are also a reminder that things operate on scales far beyond our own; that if you stretch a sheet under the stars, you will slowly gather their dust.

Paid Content - Summer Update and Sale - The Quantum Cat

2026-07-07T12:30:15.000Z

Hello!

Thanks for reading The Quantum Cat, a newsletter covering space, physics, and the exploration of both. If you have been enjoying the newsletter, I wanted to share what paid subscribers have been reading and what comes next.

Until now, paid content has consisted of additional in-depth articles every month. Over the past year, these have focused on two broad areas. One, Visions of the Cosmos, looks at the art and photography behind astronomy. The other, Physics of the Ancient World, explores how people from Ancient Greece to Babylonia understood the world around them.

Over the next few months, I plan to continue looking into these areas. Upcoming paid articles will discuss the work of Euclid, of Archimedes, and how other ancient people in India, the Americas, and Australia developed their own ideas about physics and astronomy. I will also be covering the drawings of Galileo, the astrology of Kepler, and the canals of Mars. Before all that, however, the next paid article will look at the extreme engineering necessary to send a probe closer to the Sun than ever before.

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Until next week,

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What’s New in the Paid Archives

The Week in Space and Physics: The Sign of a Passing Star - The Quantum Cat

2026-07-02T12:31:59.000Z

The corona streaming around the Moon during the solar eclipse of August 2017. Credit: Miloslav Druckmüller, Peter Aniol, Shadia Habbal/NASA Goddard, Joy Ng.

Far out in space, far beyond the orbits of Neptune and Pluto, beyond even that of Sedna, lies a vast cloud of ice and dust.

This cloud extends far around our Solar System. It is called the Oort Cloud, and although we have never directly seen it, bits of it occasionally fall into the inner Solar System. When they do, they appear as comets, tracing long orbits from the outer ice to the inner warmth. Some of them, the longest of the long-period comets, can spend a million years or more falling inwards from the Oort Cloud until the moment they appear in our skies.

Because the Oort Cloud is so big – stretching outwards for at least a light year – astronomers have long thought it should occasionally be disturbed by passing stars. At times these stars can come surprisingly close to our Sun, and when they do, their influence should upset the orbits of objects in the Oort Cloud.

Some objects will be thrown outwards. Indeed, the handful of interstellar comets we have seen may be the result of something similar happening around other stars. But some will be knocked inwards. And this should create something like a shower of comets falling towards the inner Solar System; a visible marker of passing stars that appears a few hundred thousand years after they arrive.

Data from the Gaia telescope tells us that one such star should have approached about two and a half million years ago. That star – HD 7977 – currently lies two hundred and fifty light years from Earth. But its trajectory shows that it must have passed close to us. Exactly how close is uncertain, but it may have come within a fifth of a light-year of the Sun.

That would put it well within the Oort Cloud. In a recent pre-print paper, two researchers – Nathan Kaib and Sean Raymond – modelled the effect this close passage would have had on the Solar System. Like previous studies, they found that HD 7977 would have sent a wave of comets raining down on the inner planets.

In an effort to work out how close HD 7977 came, however, they modelled different possible close approaches. They then compared the results of these models with the orbits of real observed comets. These, they found, show a pattern that can be explained if HD 7977 had passed within a tenth of a light-year of our Sun.

That is remarkably close, perhaps closer than any other star has come in the past few hundred million years. If the conclusions are accurate, then this approach could even have altered the orbit of our planet, changed the climate, and so affected the course of evolution at a critical moment for the origins of our species.

More data from Gaia will be released in the next few years. When it is, astronomers hope to better pin down the trajectory of HD 7977, and thus work out with more accuracy how close it came to the Sun. If we can do that, we can more precisely model the impact it must have had on the Solar System and on us.

If Kaib and Raymond are right, though, we are still living through the aftermath of this close approach. Though HD 7977 is now two hundred and fifty light years away, the comets we see in the sky today may still be part of a long shower triggered by its ancient passage.

Time for an Upgrade at the Large Hadron Collider

The Large Hadron Collider is a marvel of modern engineering. It is the world’s largest and highest-energy particle collider, a machine that has the power consumption of a small city, and that collides sub-atomic particles with a ferocity seen nowhere else on Earth.

This all means it can probe the laws of physics at a deeper and more fundamental level than any other scientific experiment in the world. Yet, last week, on June 29, the instruments of the Large Hadron Collider ceased work. The particle beams were shut down, the collisions put on hold, and the experiments suspended.

For the next two years, its engineers and scientists will conduct a campaign to maintain, repair, and upgrade the collider. This effort, named the Long Shutdown 3, should result in an enhanced machine. By the end, it will be capable of more particle collisions than ever achieved in the past.

Yet the amount of work that must be done to meet this goal is considerable and highly challenging. Over the next few months, operators will need to warm up the collider’s superconducting magnets. These are normally kept at a temperature just two degrees above absolute zero. Warming them to a temperature where they can be accessed and repaired takes several months alone.

Some of the new technology involved in the Long Shutdown 3. Credit: CERN.

After that, engineers will reconfigure many of the instruments and experiments deployed at the collider. One key target is to increase the luminosity of the collider – a measure, essentially, of how many collisions take place when its beams cross. The higher its luminosity, the more data the collider can gather.

This work, CERN says, will have two key benefits. First, there is the engineering knowledge gained. The LHC operates at the frontiers of our abilities, and upgrading it forces innovation in fields from superconductivity to industrial engineering. But second, of course, is the opportunity for new science.

The upgraded LHC will produce much more data on particle collisions, and offer a more stringent test of how the fundamental laws of nature operate. There is nowhere else on Earth capable of matching this ability. If we want to make discoveries about the subatomic world, this upgrade may be our best hope yet.

Euclid Paves the Way for Roman

At the end of June, the European Space Agency released the largest and most detailed image of the centre of our galaxy yet captured. It shows more than sixty million stars, almost all of them crowded into the central bulge of the Milky Way, and was captured by the Euclid Space Telescope.

In some ways, this image was an exception for Euclid. Most of its time is spent surveying distant galaxies, an effort that should help astronomers map the distribution of dark matter throughout the cosmos. Images of our own galaxy, no matter how beautiful they are, don’t do a lot to help with this goal.

But they will help support the efforts of an upcoming telescope. In August, NASA hopes to launch the Nancy Grace Roman Space Telescope. Although its domain of work will be wide, this new observatory will dedicate some of its time to monitoring the heart of our galaxy. Astronomers expect this study will help spot tens of thousands of new stars, planets, and other things like black holes.

Euclid’s operators thus accepted a special request to get an early start on this survey. Over a period of about twenty-six hours, they paused the observatory’s main work and redirected it towards the heart of the galaxy. The resulting image – both beautiful and unprecedented – offers a preview of what the Roman telescope will do, and gives astronomers an early start on their ambitious effort to monitor the centre of the Milky Way.

The bulge of the Milky Way, imaged by Euclid. Credit: ESA/Euclid/Euclid Consortium/NASA, CFHT, image processing by J.-C. Cuillandre and E. Bertin (CEA Paris-Saclay)

A Trace of Life on Mars?

Over the past two years, scientists have been investigating possible traces of ancient life on Mars. These are not fossils, or even anything close, but rather chemical and mineral signatures that may have been deposited by simple life forms living in the rivers that once flowed over the Martian landscape.

This evidence, they concluded last year, is a potential sign of life but not a certain one. The minerals, which were uncovered by the Perseverance rover, could have been created by biology. But they could also have been created by a chemical or geological process, and so far we cannot rule out that possibility.

Now, new evidence has emerged from Perseverance’s instruments. One of these, a device called SHERLOC, spotted signs of large carbon-containing molecules. These were found both near the intriguing minerals and on another rock lying about a hundred metres from it.

On Earth, such molecules are often made by living organisms. Yet they can also be made by other processes – perhaps by chemical reactions, or by the fall of a meteorite. As before, these represent a potential sign of ancient life. But the evidence is still not conclusive.

The Atom and The Void - The Quantum Cat

2026-06-23T12:31:03.000Z

The first principles of the universe are atoms and empty space; everything else is merely thought to exist.
- Diogenes Laertius on Democritus

Ours is not an empty world.

Artists sometimes speak of horror vacui, the idea that nature abhors a vacuum. Humans certainly do. Emptiness – the blank canvas, the empty page, the silent room – is somehow disturbing, unsettling, something we seek to fill with colour, with words, with sound. The empty moment is filled with idle activity; the blank sheet is covered in scribbles and doodles.

For Aristotle, this basic instinct reflected a deeper truth of reality. Nature abhors a vacuum. Create a void, he said, and the fullness of the world immediately rushes in. Emptiness cannot last; it cannot even really exist, he wrote, and the very concept of it was almost absurd. The so-called vacuum, he once joked, was itself a vacuous idea.

And yet it somehow wasn’t. Aristotle’s writings on the void have long rung hollow. Something seems off in his dismissal, in his reluctance to consider the possibility of nothingness. The root of this aversion has always been mysterious: some think it was religious in nature, or based on a conviction about natural perfection, or even just down to a dislike, common to us all, of the idea of pure emptiness.

The Garden of Earthly Delights by Hieronymus Bosch. Bosch packed his canvas with detail and symbolism, leaving very little unused space.

In the centuries before Aristotle, a lively debate had raged over the nature of nothingness. Some had found it a hard thing, almost an impossible thing, to talk about: Parmenides, writing about two hundred years earlier, had argued that since nothingness was by definition nothing, there was nothing at all you could say about it.

But there was, Leucippus and Democritus argued, a sense in which ‘nothing’ must exist. It was only through empty space, through the void, that things could move. Deny the possibility of emptiness, they said, and you deny the reality of motion and change – an idea that Zeno explored with great effect in his series of famous paradoxes.

The world they described was one filled with atomos, the unchanging and indivisible components of matter. It was these atoms that moved through the void, and that by rearranging themselves, allowed for change to occur. The necessity of the void was simple: for an atom to move, it had to both leave an empty space behind it and find an empty space to move into.

Far from finding the void abhorrent, their description made it essential. With no voids, change would become impossible. Without the atomos, the world would effectively be a blank sheet. Together, the void and the atom were thus responsible for all the fullness of existence: all the colours, all the smells, all the sounds, all the messy detail that makes up reality.

Nature, a fragment of Democritus tells us, was “by convention sweet, by convention bitter, by convention hot, by convention cold, by convention colour: but in reality atoms and the void.”

The Week in Space and Physics: A Space Station Emergency - The Quantum Cat

2026-06-17T12:32:12.000Z

Credit: NASA Johnson.

For a few hours, it seemed close to the nightmare scenario.

On June 5, mission control in Houston directed the astronauts on board the International Space Station to take emergency shelter. In a moment of high drama, five of them entered a docked Dragon capsule and began preparing for a fast and unexpected return to Earth. At fault was an air leak. The station was losing air through an ageing module, and the risks were deemed so serious that NASA ordered immediate action.

The module at fault is known as PrK. It is a small tunnel that connects the key Russian Zvezda module with a docking port. Typically, this port is used to dock the Russian Progress capsule, and the tunnel is used to transfer cargo in and out of the docked spacecraft.

But for several years, the tunnel has been causing problems. Leaks were first found in September 2019, at which time they seemed to be small and manageable. But over time they have worsened. Cosmonauts have repeatedly patched cracks with sealant, but this has not solved the problem.

To reduce the impact, the tunnel is usually closed and left unpressurised. But when cosmonauts need to access the Progress capsule, they must repressurise it. When they do, other precautions are taken – including closing other interior hatches in the station to reduce the risks of air loss.

Progress docked to Zvezda. NASA.

As cosmonauts worked in the tunnel in early June, however, they noticed an increase in the rate at which air was escaping the module. In the past, such leaks have been fixed by using a sealant. This time, however, they apparently elected to make a more radical fix. Details are sparse, but it seems two cosmonauts were planning to cut into the structure of the module to better access the leak.

As they prepared for this, the other five astronauts on board – three Americans, one French, and one Russian - took shelter inside Dragon. Controllers apparently feared a catastrophic outcome: one in which the leaks rapidly spread, the tunnel split open, and air rushed out of the station. If that had happened, Dragon would have departed. The other two cosmonauts would have escaped on a Soyuz capsule, and for the first time in two decades the station would have been abandoned.

Fortunately, however, the situation lasted only two hours. Roscosmos later said the structural repair work had been paused and the situation would be evaluated. According to more recent reports, Roscosmos has now decided to permanently close the tunnel instead of attempting the potentially dangerous repair.

Still, the event is a warning sign. The station is ageing. NASA has hinted at wanting to continue operations on the station into the 2030s, at least until the point at which a smaller replacement is available. An early abandonment of the station would sharply cut the spaceflight programs of both America and Russia. Indeed, the only remaining station would be Chinese, and that would add to the sense that America is ceding influence in space to its geopolitical rival.

For now, operators and astronauts must deal with issues as they arise. Alongside the air leaks, controllers are now dealing with problems in the station’s robotic arm. The Canadarm, they say, will need a spacewalk to get it functioning properly again.

The First of the Nuclear Clocks

The best clocks on Earth are so accurate they would not have erred by a single second in all the years since the Big Bang.

We can do better. All clocks need some kind of reference frequency to count out the passing of time. In the past this took the form of the Earth’s rotation, the swing of a pendulum, or the resonant vibrations of a crystal of quartz. Today, we use more sophisticated means.

In modern atomic clocks, the frequency is determined by electrons inside an atom. The laws of quantum physics tell us these electrons can only occupy a set of fixed energy levels. To jump from one level to another, an electron needs to receive a precise amount of energy, and this can be given by incoming radiation of a precise frequency. From this, we can obtain a natural frequency that can be used to count the seconds.

In theory this approach can track time almost perfectly. In practice, however, the world is messy and disturbances are unavoidable. This places a limit on the accuracy that can be obtained, and means that although an atomic clock could have almost perfectly counted the seconds since the Big Bang, it cannot do so forever.

Yet clocks that rely not on electrons, but on the protons and neutrons of the atomic nucleus, might do better. Like electrons, these can jump between energy levels. But they are more sheltered, which means they are less affected by external disturbances. A nuclear clock, one based on the atomic nucleus, could be more accurate than one based on electrons.

Of course, things are harder in practice. Only atoms of thorium-229, a rare isotope of a radioactive element, have proven suitable for clocks of this kind. They can be made to jump by use of a laser, though one of a difficult kind to build and control.

Recently, two teams – one in China, one in Europe – announced they had built the first nuclear clocks based on thorium-229. Although each team took a slightly different approach, they each produced clocks of similar quality. Together, they are the first to demonstrate the idea, and so prove that nuclear clocks are indeed possible.

They are not yet more accurate than the best atomic clocks. But these are early days. Future improvements should build on these initial advances, and eventually allow for even more precise counting of time than is possible today. That, researchers say, will allow us to probe reality even more closely, and perhaps to cast light on some of the deepest mysteries of time and space.

Black Hole Winds

At the heart of the Milky Way lies a supermassive black hole known as Sagittarius A*.

Like most such beasts, this black hole is surrounded by a cloud of gas, dust, and stars. Much of this is trapped in orbit around the black hole, spiralling slowly towards the point at which it will be consumed. Yet as matter falls it heats up, and this heat drives winds blowing away from the black hole.

These winds are an inevitable side-effect of how black holes feed. They cannot cease, but they can vary in power. When black holes go on a feeding frenzy, their winds strengthen into powerful jets, as seen in galaxies like Centaurus A. In galaxies like our own, where the black hole is consuming matter at a sedate pace, the winds should be gentler.

Until now, however, the winds of Sagittarius A* were missing. This is partly because the dust and gas around the black hole obscure our view of the surrounding region. Over the past five years, however, Mark Gorski and Lena Murchikova of Northwestern University have made careful observations of the gas in the centre of the galaxy.

The orange shows the gas clouds recently studied. The cone in which winds are blowing is marked, and black hole itself appears as the bright dot in the centre. Mark D. Gorski and Lena Murchikova 2026 ApJL.

With these measurements they were able to map out the region around the black hole. That revealed a gap, a cone-shaped region which seems to have been swept clear of gas. The reason, they say, must be the winds coming from Sagittarius A*.

If so, this is the first clear evidence of our black hole’s winds. More observations should tell us how fast the wind is blowing, and perhaps how it has changed over time. That should give insight into how much matter the black hole is consuming, and whether it has gone through periods of activity in the recent past.

The Silent Interstellar Comet

As far as we know, the comet 3I/Atlas is an extraordinarily old lump of dust and ice. It is remarkable for its origin: the comet was born around a distant star, and has since spent much of its life traversing the vast gulfs of interstellar space.

This alone is astonishing. Yet some imagine the comet to be something more: in particular, the astronomer Avi Loeb has spent a considerable amount of time wondering if 3I/Atlas is in fact a relic of alien technology. There is little evidence for this. 3I/Atlas looks like a comet, acts like a comet, and moves like a comet.

It also shows no signs of trying to communicate with us or anyone else. After the comet was first discovered, the SETI institute began monitoring it for signs of radio signals. Yet, as they reported earlier this month, they detected nothing. Whatever else 3I/Atlas might be doing, it is not sending messages via radio.

Of course, aliens may have access to technologies far beyond our knowledge. Yet in the absence of any compelling evidence at all, we should conclude that 3I/Atlas is what it appears to be: a remarkable but completely natural comet.

The Week in Space and Physics: Voices From The Moon - The Quantum Cat

2026-06-04T12:31:29.000Z

The far side of the Moon, as seen by the crew of Artemis II. Credit: NASA.

“The next time the world tunes in to watch astronauts fly around the Moon”, NASA boss Jared Isaacman said on May 19, “they will be taikonauts”.

China has not yet announced any such mission, which would likely replicate either Artemis II or Apollo 8. But it is not really in doubt that such a mission is coming, and that it may happen soon. Over the past few months, China has conducted tests of both its crew capsule, Mengzhou, and of its Long March 10A booster, the rocket that will propel astronauts towards the Moon.

Patches from the Mengzhou in-flight abort test. Via China In Space.

For American politicians, the possibility that China might beat America back to the lunar surface is of deep concern. Isaacman has responded to these worries by pushing NASA to move faster and to start building out a base on the surface. America, he has said, “will never again give up the Moon”.

Artemis IV, the mission which might see Americans leave footprints on the Moon for the first time since 1972, is now scheduled to take place in 2028. If it launches on time, or at least before 2030, America has a good chance of beating China to the lunar surface.

Unfortunately, the past month saw two big setbacks in America’s efforts to do this. First was the twelfth launch of SpaceX’s Starship rocket. NASA plans to use this as a landing craft, the vessel that will take astronauts on the final leg of the trip to the surface and back. SpaceX, however, has struggled to get Starship ready in time.

May’s flight was supposed to change things. Over the past few months, SpaceX’s engineers have built an improved version of Starship, one they call V3. It is supposed to fix many of the issues that bedevilled the previous version, and so clear the way towards attempting a Moon landing.

Yet the test flight showed only mixed results: during ascent the rocket suffered from failed engines, and SpaceX was unable to steer the booster back to its target splashdown point. As the upper stage, ‘the ship’, flew on, it too suffered from engine problems. SpaceX abandoned some of their planned tests, though they did manage to demonstrate the ability to deploy dummy satellites. The ship at least made it back through the atmosphere in one piece, and came to a partially controlled ‘landing’ before it toppled into the ocean.

The next test flight may do better. But it is inescapable that things are not going as well as hoped. After twelve flights, SpaceX appears stuck, doomed to endlessly repeat the same suborbital trajectory with mixed results. To get to the Moon they need to break out of this loop. If it wants to get there before China, Starship almost certainly need to reach a proper orbit sometime this year.

In recent months, NASA seemed to be building a backup plan. This would have used a lander built by Blue Origin, a company owned by Amazon founder Jeff Bezos. But last week Blue suffered a major setback of its own. While their New Glenn rocket was undergoing tests in Florida, it suddenly and dramatically exploded in an enormous fireball.

The surrounding launch facilities have been badly damaged. How much this will set things back remains unclear – but it is clearly a serious blow. It would be a surprise if Blue Origin is able to launch again this year. As a result, it may not just be the next voices from the Moon that are Chinese. The next footprints may be too.

The Snowball Earth

Our world has not always been blue and green. For a while it was purple: the earliest photosynthetic life might have used retinal instead of chlorophyll, and this would have given the planet a purplish tinge. Later – during a long stagnant period geologists have nicknamed the Boring Billion – other creatures may have turned the oceans a milky black.

Around six hundred million years ago, some scientists think the Earth became a snowball. Ice sheets would have crept outwards from the poles, and eventually covered almost the entire planet. The equator would have been as cold as Antarctica is today, and even if it wasn’t frozen, the tropics would at least have been covered in an icy slush.

In theory, this kind of frozen world is perfectly stable. Ice reflects sunlight and heat, and this forms a feedback loop that keeps the planet cold. Global ice sheets may have emerged on multiple occasions, stuck around for millions of years, and only receded as something – volcanoes or meteor impacts perhaps – created enough warming to knock the world into a different stable climate.

Since then, however, the ice sheets have either vanished completely – as they did in the Jurassic period – or stuck around the poles, where they are found today. For some reason, Snowball Earths don’t seem to happen any more.

There are two possible explanations as to why not. One theory suggests that something has changed, and thus made global glaciation impossible. But others argue that supporters of the Snowball Earth are simply wrong, and that our planet has never frozen over entirely.

In a recent study, Erica Bisesi of the Astronomical Observatory of Trieste tested the first idea by modelling the conditions that may have prevailed on the Earth during such a snowball scenario. The last time it happened, she points out, the landmasses were fused into a single supercontinent named Rodinia that straddled the equator. Plants and trees had not yet emerged, so this continent was bare and rocky.

That would have made the Earth more reflective. The Sun was also cooler in the past, and half a billion years ago our planet would have received about five percent less heat than it does today. Together, these two factors would have made the world colder, Bisesi says, and more susceptible to falling into a snowball state.

But when that state ended, and the Earth warmed again, the temperature shift may have provided the spark for a more radical change. As the ice sheets melted, the flow of sediments and nutrients they sent into the warming oceans would have allowed life to flourish. Perhaps, some have wondered, the last time this happened it helped spark the Cambrian Explosion, the moment when life rapidly became much more complex.

That, Bisesi says, tipped the scales. As the continents began to be covered in vegetation, they reflected less sunlight. A darker planet absorbed more heat, and that may have been enough to prevent it from ever freezing over again. Once the world turned blue and green, in other words, it may have been just stable enough to stay that way.

Webb Images a Hellish Landscape

A group of astronomers led by Sebastian Zieba of Harvard reported using the James Webb Space Telescope to directly measure the surface of a distant world. Their target, a planet called Kua’kua, lies about fifty light years away. It orbits a red dwarf, a star fainter and cooler than our own, and it is slightly larger than the Earth.

It is not, however, a nice place. Measurements reported in 2019 showed it to be an airless and hot world. Its orbit lies close to its star, and it is tidally locked – which means one side of the planet is forever turned towards the star, while the other perpetually stares out into space. This starward side is extremely hot, soaring to about 1500 degrees Celsius.

Since it has no atmosphere, telescopes like the James Webb can directly measure properties of its surface. Zieba and his team did this, using the telescope to study the rocks and minerals scattered across its terrain. These observations showed it to be a barren place. Its surface is ancient, covered in volcanic regolith, and has likely suffered under billions of years of impacts and stellar radiation.

This means it looks more like Mercury, or perhaps the Moon, than like Earth or Mars. That, given the extreme conditions of Kua’kua, was not unexpected. But other worlds could still offer surprises. The presence of different minerals and rocks can reveal how active a planet’s geology is. And the more dynamic a world is, the more interesting it will be - and the greater the potential for it to host some kind of primitive life.

Psyche Swoops Past Mars

On May 15, NASA’s Psyche probe swung past Mars. The Red Planet is not the spacecraft’s ultimate destination: it is designed to study 16 Psyche, one of the largest asteroids in the belt between Mars and Jupiter. But to get there it needs energy, and it thus used this brief visit to Mars to gain acceleration through a gravitational assist.

Psyche approached Mars from the opposite direction of the Sun. This gave it a view of the planet that we rarely see. In the images it sent back, the Red Planet appears as a crescent, the Sun is almost exactly behind it, and only a sliver of the world is illuminated.

Psyche’s operators used the encounter to test out the instruments and cameras on board the spacecraft. All seems to have gone well, and the team say they captured thousands of observations of Mars. Their next milestone will come in 2029, when Psyche finally reaches its namesake in the asteroid belt.

The crescent of Mars, imaged by Psyche. NASA/JPL-Caltech/ASU.

The Week in Space and Physics: The Best Way To Alpha Centauri? - The Quantum Cat

2026-05-20T12:31:27.000Z

The Trifid Nebula, imaged by Hubble. Image: NASA, ESA, STScI; Image Processing: Joseph DePasquale (STScI)

The stars are far, almost unimaginably so.

In 1970, as the crew of Apollo 13 fell back towards Earth, they briefly hit a speed of almost twenty-five thousand miles per hour. This is the fastest humans have ever travelled. Even Artemis II, returning from the Moon in April, fell about a thousand miles per hour short of this record.

Had the Apollo 13 capsule been capable of maintaining this speed, it could have looped around the planet in an hour, returned to the Moon in less than half a day, and then gone on to cross the orbit of Mars within a few months. But even at this rate, it would still have taken more than one hundred thousand years to reach Proxima Centauri, the closest star to our own.

As a result, dreams of interstellar travel are often just that. Indeed, there are few technologies that might allow us to span the gulfs of interstellar space. Yet the idea is not completely out of the question. There are a handful of stars within a dozen light-years of Earth. Crossing such a distance is just about feasible, at least according to the team behind Breakthrough Starshot.

They reckon that rather than sending a single big spacecraft, we might be better off sending a swarm of tiny ones. Thousands of these could be launched together. Each would deploy a light-sail, a device that uses the slight pressure of sunlight to create a small but steady acceleration.

This would not normally be fast enough to reach the stars. But Breakthrough Starshot thinks we could accelerate probes faster by using laser beams in place of sunlight. Fire these at small and lightweight spacecraft, they say, and we could get them to a reasonable fraction of the speed of light. Of course such speeds are dangerous - even minor collisions would obliterate a probe - but numbers can compensate for these risks.

To study how such a mission might work in practice, a team led by Marshall Eubanks of Space Initiatives looked at what a swarm of one thousand small spacecraft could do. They imagine accelerating them towards Alpha Centauri at twenty percent of the speed of light. At this rate, they could reach the star system in about twenty-one years.

The road to Alpha Centauri. Charles Carter/Keck Institute for Space Studies.

As they flew through the outer solar system and into interstellar space, however, they would already begin sending back valuable scientific data. At first, they might hunt for planets and dwarf worlds hidden at the edge of the solar system. Later, they could map out the density of interstellar dust, hunt for primordial black holes, and even probe fundamental theories about gravity and about space and time.

The probes would still be travelling at high speed as they reached Alpha Centauri, and would have limited capacity to decelerate. But they would be able to image the planets around the three stars found there, and could look for moons and other objects. Instruments could scan these worlds, image their surfaces, and look for signs of life or other interesting processes.

All this, they conclude, is not only possible to do, but may be the only reasonable prospect for interstellar travel in the coming century. The benefits would be astonishing: swarms could visit half a dozen nearby stars, fly out to rogue planets, and explore the most distant regions of the solar system. But the challenges of making this real should not be understated. At the very least, it will take far more money than anyone has so far seemed willing to venture.

The Clouds of Interstellar Space

Every day, several tons of dust fall upon our planet. Most of it comes from the solar system, in the form of tiny fragments of passing comets, the debris of ancient impacts, and the leftover material from the birth of the planets. But some comes from further afield.

As the solar system moves through the galaxy, it periodically passes through clouds of interstellar dust and gas. About fifteen of these clouds are scattered around us at the moment , and as our system moves through them, it is sweeping up some of the dust they contain.

Bits of this dust eventually make their way to Earth. Although much of it is then simply incorporated into our world, some of it builds up in layers at the bottom of the ocean or in the polar ice sheets. And there, as a recent study found, it can act as a tracer for the history of our star’s long voyage through the galaxy.

NASA/Goddard/Adler/U. Chicago/Wesleyan

The study, led by Dominik Koll of the Australian National University, analysed polar ice formed between forty and eighty thousand years ago. They found that the amount of cosmic dust falling on Earth seem to have increased since that time, possibly because we have recently entered an interstellar cloud.

That would fit well with ideas about our solar system’s recent trajectory. It is currently in the ‘local interstellar cloud’, and probably moved into this cloud sometime in the last hundred thousand years. We are currently heading towards its edge, and at some point in the next few millennia we should enter the nearby ‘G-Cloud’.

Much more work remains to be done. Other sources of dust have been found on the Moon, as well as in oceanic sediments. Together they paint a history of several supernovae erupting in our region of space over the past few million years, and tell a story of how we have moved between the clouds and bubbles sculpted by these violent events.

Getting all of this together into a single cohesive narrative will take time. But once complete, it will reveal the history of our long cosmic journey.

Artemis III

After this year’s successful flight around the Moon, NASA is moving ahead with plans for the third Artemis mission.

Originally, this was supposed to put astronauts on the lunar surface, and would have been the first time anyone had set foot on the Moon in more than five decades. But although NASA now has a rocket and a capsule, it does not have a lander ready to take crews to the surface and back.

NASA was relying on SpaceX to provide this lander. Under contracts awarded in 2020 and 2021, SpaceX was supposed to develop their Starship system to support lunar landings. But progress has been slow, and Starship still isn’t capable of getting anywhere close to the Moon.

With Artemis II complete, NASA has been forced to recognise this reality. Instead of going to the Moon, then, Artemis III will remain in a low orbit around the Earth. To salvage some value from the mission, NASA will practice docking the Orion capsule with Starship. In future missions this step will be crucial, as the two spacecraft are supposed to meet in lunar orbit to allow astronauts to transfer from one vehicle to another.

But in what may be a subtle warning to SpaceX, NASA is also hoping to demonstrate docking with a second lunar lander. This one, being built by Blue Origin, could provide an alternative route to the Moon, and give NASA a backup option if Starship simply is not ready in time.

Saving Swift: A Race Against Time

Since 2004, the orbiting Swift Observatory has been studying the mysterious Gamma Ray Bursts that appear in the distant universe. Although the mission was supposed to last just two years, it is now approaching its twenty-second anniversary in space. In that time, it has carried out more then eight hundred thousand measurements.

Unfortunately, Swift is also on the verge of death. It was originally launched into an orbit six hundred kilometres high, but over the last two decades the atmosphere has dragged it back down. It has now fallen below an altitude of four hundred kilometres and if nothing is done, it will make a fiery re-entry in the next few months.

A map of the first five hundred Gamma Ray Bursts spotted by Swift. NASA/Swift/Francis Reddy.

Last year, however, NASA partnered with a company called Katalyst Space Technologies. Together they have built a spacecraft that could grab Swift and then boost it into a higher orbit. That would save the telescope, and give it another few decades of life.

NASA recently announced this new spacecraft has completed tests on the ground. It will now move towards a launch – possibly as soon as early June – and then start a race against the clock to raise Swift before it falls too low into the atmosphere.

If this works, it would demonstrate an important ability to grasp and raise the orbits of falling satellites. Swift is not the only one of NASA’s telescopes that is in peril of re-entry: Hubble, launched in 1994, is now losing altitude at a rapid rate. If nothing is done, it will burn in the early 2030s. Katalyst’s mission, if it is a success, may offer a way to prolong Hubble into the 2040s and beyond.

An Atmosphere and a Puzzle Beyond Pluto - The Quantum Cat

2026-05-15T12:31:09.000Z

The blue haze of Pluto’s atmosphere, as photographed by New Horizons. NASA/JHUAPL/SwRI.

For most of its known history, nobody has cared much about 2002 XV93. It is a small world lying somewhere just beyond the orbit of Pluto, one presumably covered in a grey and gritty kind of ice, and a place considered so unremarkable that no one has bothered to give it a proper name.

Yet as of last week, 2002 XV93 is suddenly famous. It is, according to a recent discovery, one of the most distant places in the solar system known to host an atmosphere. Truth be told, it is not much of an atmosphere. The small rock measures only a few hundred kilometres across, and the layer of gas surrounding it is at least ten million times more tenuous than the air around our planet.

But that is at least something. And its presence defies our expectations about what the worlds beyond Neptune should look like. All those known to us are icy, frozen objects. Most are small. A few are big enough to be notable: Pluto, for example, was long a member of the exclusive club of planets. Eris is slightly more massive than Pluto, and others – Haumea, Makemake, Sedna – measure more than a thousand kilometres across.

In this image taken by New Horizons, Pluto’s atmosphere appears as a perfect blue ring surrounding the shadow of that distant world. NASA/JHUAPL/SwRI

Some of these larger places do have atmospheres. That of Pluto, for example, is a thin layer of nitrogen that appears as a bluish haze stretching over its surface. Traces of methane have been found around Makemake. But others are more elusive. Eris and Sedna, though both large, show no sign of an atmosphere.

That may be because they are much further away – roughly twice as far as Pluto – and thus extremely cold. Any atmospheres these two dwarf planets did possess have surely escaped or condensed into ice. Over the next few centuries, Eris will swing inwards towards the Sun and gently warm. As it does, this ice may sublimate, and the frozen world might regain a thin and temporary atmosphere.

But this should really be the limit. Smaller worlds, those less than about a thousand kilometres across, are not expected to maintain any kind of atmosphere. They lack the gravitational strength to hold on to a layer of gas. If they ever had any, it should thus have long ago escaped into space or frozen to their surfaces.

Yet 2002 XV93 seems to differ. It measures about five hundred kilometres (three hundred miles) across, and so should fall into the category of small, insignificant places unworthy of carrying around a layer of gas. The question is thus twofold. Does it really have an atmosphere? And if it does, how did such a small world manage to keep it?

A Stellar Occultation

The story of 2002 XV93’s atmosphere begins on January 10, 2024. On that day, the small world passed briefly in front of a star in the constellation Auriga, thus creating a kind of mini-eclipse. Astronomers call such events stellar occultations, and they happen whenever a planet or something else in our solar system crosses in front of a more distant star.

Occultations can reveal surprising details about these objects. As a world starts to move across a star, it darkens the light coming from it. If the world lacks an atmosphere, this darkening will be abrupt, caused by the sudden passing of a solid surface between us and the distant star.

But if the body is instead surrounded by gas, the starlight will fade more gradually. The atmosphere may bend and filter the light, changing its colour in response to the gases present there. As the occultation ends, and the world moves on, this pattern will play out in reverse.

Careful study of exactly how the brightness of a star varies during an occultation can thus reveal whether a world has an atmosphere or not. As an example, it was thanks to this technique that astronomers knew Pluto had an atmosphere well before New Horizons arrived and took photographs. By comparing multiple occultations spread over many years, they could even watch this atmosphere expand and contract with the changing seasons.

On the left, occultation data from Pluto (Sicardy et al). It shows a gradual fade as the occultation begins and ends. On the right, data from Eris (Sicardy et al, 2011). It shows a sharp fade at both the start and end.

The 2024 occultation of 2002 XV93 was observed from Japan. A team led by Ko Arimatsu of the National Astronomical Observatory of Japan set up three stations to take measurements of the event. Though they expected to see a sharp pattern, one more resembling that of the airless Eris rather than that of Pluto, the occultation instead showed the brief signs of a layer of gas.

The results, Arimatsu said, came as a surprise. When they analysed the data, they found it showed signs of a thin but clearly present atmosphere. It is tenuous and has a pressure at least five million times lower than that on Earth at sea level. Indeed, to reach a comparable pressure in our atmosphere you would have to ascend hundreds of miles into our faint and rarely visited exosphere.

Occultation data from 2002 XV93. Rather than an abrupt darkening, the starlight faded gradually as the object crossed in front of it. Image: P1X3LZIMMY, Data: Arimatsu et al, 2026.

A World of Ice Volcanoes?

The fact this layer exists at all is hard to explain. 2002 XV93 is so small that even a slight atmosphere should have been lost into space within a few centuries. That we can still see it today suggests something must have recently refilled it, and this tells us this small world is more dynamic than it at first appears.

Some objects beyond Neptune do show signs of atmospheres coming and going. Unlike the Earth, these worlds can follow eccentric paths: Pluto, for example, swings in and out along its long voyage around the Sun. At its closest, it passes within the orbit of Neptune. At its most distant, it is almost twice as far away.

This leads to drastic changes in temperature. Whenever Pluto moves towards the Sun, as it was doing until 1989, it warms up, its ices sublimate, and its atmosphere grows. As it moves away, as it is now doing, it begins to cool again, the gases in the atmosphere condense, and the layer of gas fades away.

Eris, which follows an even more eccentric orbit and is currently much further away, will likely show a similar pattern as it draws closer to the Sun over the next few hundred years. But there is no real sign the same is happening on 2002 XV93: indeed, measurements have found no traces of the kinds of ice on its surface from which an atmosphere could emerge.

Instead, Ko Arimatsu and his team think there are two better possibilities. One is that the world has experienced a recent collision. This would have thrown up a cloud of dust and ice and allowed a temporary atmosphere to form. It will eventually be lost, but it might well stick around for a few decades or centuries.

Ice volcanoes on Pluto? The regions marked in blue appear to show signs of cryovolcanism. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Isaac Herrera/Kelsi Singer.

Alternatively, 2002 XV93 may be home to the phenomenon of cryovolcanism. Though it has a solid and frozen surface, underneath it may have a partially liquid layer. If something is heating this – possibly the tidal force of an unseen satellite, or perhaps a series of small impacts - then this layer could remain liquid. At times, it may be bursting outwards, forming a kind of ice volcano.

We have seen things like this on Pluto. Data sent by New Horizons showed signs of recent eruptions, and its images showed massive features that may have been formed by such volcanic events. We have no clear evidence of anything like this happening on 2002 XV93, but its thin atmosphere offers a hint that volcanoes might be erupting there too.

Whatever the answer is, one thing is clear. The worlds of the outer solar system – from its giants like Pluto and Eris, to its minnows like 2002 XV93 – are far more interesting than they at first appear. They are dynamic worlds, subject to forces and processes so alien and so familiar to us on Earth. They are worthy of attention – and in the case of 2002 XV93, a proper name as well.

Seizing The Light: The First Photographs Of The Heavens - The Quantum Cat

2026-05-10T12:31:40.000Z

In 1839, Louis Daguerre took the first photograph of the Moon.

The details of this image have been lost to the mists of time. A fire destroyed the laboratory and much of the work of Daguerre just weeks after it was made. The photograph of the Moon was one of those reduced to ashes. Yet, it still proved it could be done, sparked a series of excited debates at the French Academy of Sciences, and laid the foundations for the age of astrophotography.

Until that moment, indeed, all astronomy was done by hand. Since the age of Galileo, astronomers had peered through telescopes and spent painstaking hours sketching what they saw. The results were sometimes beautiful. Galileo’s watercolours of the Moon are impressive both for their simple elegance and for what they revealed about the universe.

Yet, they took time, they invited error, and they relied on the accuracy of the human eye. This was not always to be trusted: Schiaparelli believed he could see artificial lines criss-crossing Mars, the result, he thought, of an advanced engineering project. Others convinced themselves that the Red Planet periodically darkened and lightened, probably, they thought, because plants were growing in the summer and fading in the winter.

In comparison to all this, Daguerre’s technique appeared almost magical. True, it was not the first method of photography: that honour belonged to another Frenchman, Nicéphore Niépce. But Niépce’s process was slow, and sometimes needed a plate to be exposed for days to form an image. Daguerre’s was fast: it could capture an image in seconds.

When the scientists of the French Academy heard what he had done, they were giddy with excitement. Imagine, François Arago said as he announced the work, how this invention could speed up the study of Egyptian hieroglyphics, preserve treasures that would otherwise be lost, and allow the detailed examination of light itself.

For astronomy, the potential seemed great. The camera might, Arago hinted, be the greatest asset to the field since Galileo and his telescope. A revolution had followed that invention, and with Daguerre’s process, science might once again be on the cusp of great and unforeseen discoveries.

Soon after Arago’s speech, the rights to the Daguerreotype process were purchased by the French government. They awarded Daguerre a lifelong pension, elected him as an honorary academician, and later inscribed his name upon the Eiffel Tower. His process was given to the world, published freely, and made available to anyone who wished to use it1.

John William Draper / NYU Archives / Smithsonian / Processed by Alastair Williams. Source: Earth’s Moon (1840).

At the time of the announcement, the American Samuel Morse - he of the telegraph and famous code - happened to be in Paris. He quickly arranged to see the invention in person, and went to meet Daguerre at his residence. The introduction impressed him, and he apparently asked the Frenchman about the possibility of using it to take portraits.

After he returned to the United States, Morse teamed up with a chemist and doctor named John William Draper. The question of portraits still intrigued him, and as an experiment the pair opened a gallery in New York. They charged $5 for a picture - a high sum at the time - yet still attracted many of the city’s elite.

Indeed, the idea quickly proved popular: with a few years everyone from Abraham Lincoln to the Queen of England had posed for the camera. Yet Draper is also remembered for something else: in early March of 1840 he climbed to the roof of New York University, and shot a series of images of the Moon.

Getting it in focus was apparently difficult. Many of the earlier attempts, probably including Daguerre’s lost image, had shown little more than a blur of light against a dark background. But though the details are faint in Draper’s image, the surface of the Moon can be seen, along with its craters, the curves of mountain ranges, and its wide plains or mares.

This is often said to be the oldest surviving photograph of the Moon. There is some debate about that. Draper took many other photos of our satellite, and announced he had succeeded in capturing one several days before this one was taken. But those images have since been lost. This version was likely taken on March 26, 1840, a night upon which the Moon was in its last quarter.

The Week in Space and Physics: The Origins of an Interstellar Comet - The Quantum Cat

2026-05-06T12:30:48.000Z

The interstellar comet. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist.

Where did the comet 3I/Atlas come from?

It was not born in our solar system. Instead, the comet came from the stars: it is passing through our system of planets at high speed, moving so fast that although the Sun has deflected its path, it cannot hold on to the comet. 3I/Atlas will, in the years to come, fly outwards, escape the Sun’s gravity, and then drift on alone through the galaxy for another million years or so.

Based on its trajectory, speed, and direction, astronomers thought 3I/Atlas was probably ancient. It may have come from the halo of stars surrounding the Milky Way. If it did, then the comet could be extremely old indeed, and might have been born around an earlier generation of stars.

At the end of last year, as the comet approached the Sun, astronomers measured the gases streaming off it. Although this showed the object was clearly a comet, it also appeared unlike any other we have seen before. Some of these strange characteristics can be explained by its long and cold voyage through interstellar space. But others are clues pointing to its ultimate origins.

One such clue is the amount of deuterium present in the comet. This is a form of hydrogen. But where normal atoms of hydrogen have a single proton in their nuclei, deuterium atoms have both a proton and a neutron. This makes them heavier than other hydrogen atoms, and subtly influences their chemistry. The ratio of deuterium to hydrogen should be fixed when the comet first forms, and this ratio can thus tell us about the environment in which it was born.

Deuterium is rare. Plenty of hydrogen is present in the Earth’s oceans, especially in the form of water. But for every six thousand atoms of hydrogen in the oceans, there is only one of deuterium. This gives the ratio of deuterium to hydrogen on Earth, and as with the comet, this ratio hints at the origin of our water.

At low temperatures, chemistry tends to favour deuterium over hydrogen when forming water molecules. At higher temperatures, this relationship reverses. This means that when water is created in cold places – for example, at the edge of the young Solar System – it contains a higher fraction of deuterium than that of the gas from which it formed.

Deuterium in the solar system. The gas giants are made of primordial gas and show a lower ratio of deuterium to hydrogen than the asteroids, comets, and oceans of Earth. Credit: ESA, data from Altwegg et al. 2014.

This seems to be the case with the Earth’s water. The measured ratio of deuterium to hydrogen is much higher than that found in the primordial material of the solar system. Most likely, then, our water originally formed somewhere very cold – perhaps beyond the orbit of Pluto – and then fell inwards as a long and hard rain of comets and asteroids.

The measurements of 3I/Atlas found an even more extreme case. It has a lot of deuterium, at least forty times the level seen on Earth, and thirty times more than that seen in any other comet. This tells us the comet likely formed somewhere very cold, and probably under very different conditions to those found in our solar system.

But exactly where is still elusive. Astronomers cannot trace its path, at least not for more than a few million years. Comet 3I/Atlas is far older than that. The hints we have, deuterium included, only tell us it came from a very different place, and a very different age, to the one in which we were born.

Big G: Measuring Gravity

In 1797, an Englishman named Henry Cavendish set out to weigh the world.

He did this by suspending a rod from a wire. At each end of the rod he attached small lead balls, and then arranged for a pair of larger spheres to be placed near each. The result was a small deflection in the rod, a twisting motion caused by the slight gravitational attraction between the small and large balls.

By careful measurement, Cavendish was able to calculate the strength of this gravitational force. From this, he could deduce the density of the planet. The result was remarkably accurate: today’s accepted figure is 5.514 g/cm³; Cavendish, at the end of the eighteenth century, found it to be 5.448 g/cm³.

Cavendish’s diagram of his experiment.

His experiment also gave us a way to measure the strength of gravity itself. Mathematically, this is given by a constant called Big G. It relates the strength of attraction two objects will feel with both their masses and the distances between them. The higher Big G is, the stronger this force will be.

This is a number of immense interest to science. The force of gravity dictates much of the world around us: it determines how fast planets move around their stars, keeps satellites in orbit, and crushes atoms to power the reactions in the core of the Sun. Big G is key to all of this, and the more accurately we can measure it, the better we can understand our world.

Big G stands at the heart of Newton’s Law of Universal Gravitation.

Yet doing so is hard. One problem is the weakness of gravity: the deviations it produces are slight, and hard to measure with accuracy. Another is the impossibility of shielding. There is no way to block gravitational influences, and so a passing truck, a nearby herd of sheep, or even a leaf blowing in the wind can all disturb the experiment.

As a result, we don’t know Big G very well. Things have improved since Cavendish’s day, at least slightly, but almost all the other fundamental constants are known with more accuracy. Scientists have tried many ways to change this, but in recent decades experiments have added more confusion than clarity.

The problem is, they find subtly different results. This is probably down to noise, the difficulty of measurement, and other errors. But the overall result is to add uncertainty, especially since we do not always know how big these errors are, and this leaves us in the dark about the true value of Big G.

In an effort to change this, Stephan Schlamminger, a researcher at NIST, dedicated himself to replicating an earlier experiment. If he could get the same answer as they did, then it might settle the question. Unfortunately, he did not. Instead he found several previously unrealised sources of error, and set about removing them.

The result, published in April, was yet another possible value of Big G, in this case, 6.67387x10^-11 meters³/kilogram/second². That doesn’t solve the problem. But it might bring us a little closer. After all, every experiment adds a new data point, and contributes a little to the weight of evidence.

The End of Space Tourism?

A few years ago, it looked as though the long-promised era of space tourism was finally upon us. Two companies – Blue Origin and Virgin Galactic – had begun sending wealthy passengers to the edge of space. Their founders, the billionaires Jeff Bezos and Richard Branson, engaged in an unsightly race to be the first to fly beyond the upper atmosphere. Branson won, but only by a few days.

Since then, Blue Origin has flown seventeen commercial crews beyond the official edge of space. Virgin Galactic has sent seven, each to a slightly lower altitude than Blue Origin. But today, these flights are over.

Blue Origin paused their flights earlier this year. Officially, the company says this is temporary, and it simply wants to devote staff to other projects, including a crewed moon lander. But it also looks unlikely they will resume launches any time soon.

Virgin Galactic, on the other hand, has not flown since 2024. Back then, they retired their spaceplane, and said they were working on a new ‘Delta class’ vehicle. Details have since been limited, but last week they released photos of a new craft outside a hangar.

Virgin Galactic will probably want to fly this spacecraft in at least a few test flights this year. According to the company’s official statements, it should be ready to carry tourists early next year. If it makes it, then the spluttering age of space tourism might get a bit of a boost.

A Hint of New Physics

Over the past decade, researchers at the Large Hadron Collider have been tracking a slight anomaly in the decay of a group of subatomic particles called B mesons.

These particles are formed as the collider smashes together protons. They don’t last for long: within a fraction of a second they decay, or transform, into other particles. There are many possible combinations of particles that can result from this process. But in the one of interest, the B-meson decays into a kaon, a pion, and two muons.

To probe the laws of subatomic physics, researchers study the energies and angles at which particles emerge from collisions like these. The Standard Model of particle physics, our current best understanding of the subatomic world, gives predictions for what should happen.

Yet experiments have persistently shown the reality of this particular B meson decay to differ from these predictions. That could hint at something unknown happening, such at the presence of new types of particles.

But it could also be a statistical fluke. Despite more than a decade of study, the evidence remains weak. Indeed, these kinds of anomaly do occasionally appear, but usually fade away with more data. But, in April, a study found that in this case the more data we get, the stronger the argument seems to become. If that continues to hold true, the B meson could end up being the doorway into a new theory of nature.

A Nuclear Ship For Mars: Making Sense of Space Reactor Freedom - The Quantum Cat

2026-05-03T12:31:28.000Z

No one has ever built an interplanetary nuclear ship, so all we have are concept drawings like this one of a proposed mission to Jupiter. Credit: NASA.

The way NASA tells it, Space Reactor Freedom sounds simple.

This reactor, of course, is a nuclear one. NASA has apparently obtained one, or at least is close to doing so, and has also found a supply of fuel. Fortunately, they also have an electric propulsion system, one they salvaged from a failed project to build a lunar space station. The two, they say, could be bolted together to form a functional spacecraft.

With that done, the whole thing will be fired off to Mars, where it will presumably spread Freedom. This is all so easy that the agency thinks it will be ready by the end of 2028, an extraordinary pace for any government program. Afterwards, mission accomplished, Space Reactor Freedom will act as a guide for a future stream of atom-powered probes heading out to the planets.

The catch, however, is that no one has done anything like this before. The United States last launched a nuclear reactor in 1965. It never left Earth orbit, failed after six weeks, and then partially disintegrated fifteen years later. Whatever debris remains is both radioactive and likely to continue circling our planet for the next thousand years or so1.

True, the Soviets did make more serious efforts to develop the technology. Between the 1960s and 1990s, the USSR launched more than two dozen reactors, most of them short test missions. Each was shut down after a few weeks, and they were then boosted into high orbits to allow their radioactivity to decay safely away before re-entry.

Yet in 1977, one of them, a satellite named Kosmos 954, failed within weeks of launch. Finding themselves unable to boost the spacecraft or to jettison its reactor, the Soviets issued secret warnings that the satellite was out of control and falling back to Earth. Four months after launch, it hit the atmosphere over Canada, exploded, and rained radioactive debris across the Northwest Territories.

But even when it worked, the Soviet program restricted itself to niche applications in orbit. No one has ever sent a nuclear reactor into deep space, or sought to unlock the great potential the technology could offer when pushed beyond the Moon.

In many ways, that is a shame. Indeed, space agencies believe that nuclear spacecraft can push aside a lot of the constraints that hold back interplanetary travel. They can go fast, head deep into the Solar System, and carry power-hungry instruments. A nuclear probe could cut the journey time to Mars to mere weeks, carry out a detailed exploration of Saturn or Neptune, and even flit between the icy worlds of the Kuiper Belt.

All we need, if you listen to NASA, is a successful demonstration. And that is what Space Reactor Freedom is all about.

The Reasons To Go Nuclear

To get anywhere in space, you need energy.

Traditionally, this has come from chemical means: rocket engines use various chemicals as fuels, react them to produce gases, and then force them out of a nozzle. The resulting exchange of momentum pushes the spacecraft in the desired direction, rather like a sophisticated balloon carefully releasing its air.

This works, but it can be inefficient. Heavy spacecraft, especially those that head deep into the Solar System, need a lot of energy to propel them. That implies they need to carry a lot of chemical fuel. But the more they carry, the heavier they become; the heavier they get, the more fuel they need. This can quickly turn into a vicious cycle of diminishing returns, one in which every gram of extra fuel simply adds more mass and demands yet more fuel.

Engineers have a few ways around this problem. One is to make use of clever tricks like gravitational assists. These happen when a spacecraft flies past a planet in just the right way to get a kick of momentum, a boost that offers a free acceleration. But they come at the cost of time: Europe’s JUICE mission, for example, is in the midst of a six-year period bouncing between Earth and Venus. Only in 2029, once it has built up enough speed, will it head to its final destination of Jupiter.

A second option is to use more efficient fuels. Hydrogen, for instance, is a good choice: it is lightweight, it reacts strongly and releases plenty of energy, and, in the form of water, it is abundant on Earth. Rocket engines sometimes react it with oxygen, a process that results in hot steam and that can work more efficiently than almost any other chemical engine.

Yet even hydrogen pales in comparison to nuclear fuel. Instead of forging and breaking molecular bonds, nuclear fission splits the atom and unleashes immense energies. A uranium-based reactor produces at least a million times the energy of the hydrogen-oxygen reaction. In spaceflight, where every gram of mass must be carefully accounted for, this is game-changing.

Spacecraft equipped with nuclear engines can avoid the planetary dance taken by missions like JUICE. They can fly direct, and they can take more mass with them. The reactors provide copious power on arrival, and can run day and night. For a rover on Mars, a base on the Moon, or an explorer of Titan, this kind of capability is essential.

The Nuclear Electric Motor

There is no real shortage of ideas of how to make use of this power in space. Indeed, mad scientists have dreamed up a dozen insane variants of the nuclear engine. One concept involved chucking atomic bombs out the back of a spaceship and riding their shock wave out to the stars. In principle it works. In reality this would be impossible to control, hazardous to literally everyone, and a dangerous lunacy to even think about trying.

More sensible is the radioisotope thermoelectric generator. This a device that relies on radioactive decay. It is fuelled by some kind of nuclear material – plutonium-238 is a common choice – and simply uses the heat produced by its decay to generate electricity.

Generators like this are sometimes used for flights into the outer Solar System. Beyond Jupiter, the Sun’s rays fade rapidly, and so solar power cannot keep distant probes running. Radioisotope generators can – and they have been used in missions like Cassini to Saturn, the Voyagers and Pioneers, New Horizons to Pluto and beyond, and on rovers on Mars.

But these are relatively simple nuclear devices, and rarely used for sustained propulsion. Space Reactor Freedom follows an alternative model, that of nuclear electric propulsion. Rather than rely on radioactive decay, it will use a reactor to create a controlled chain reaction. This produces a supply of heat, and that is then converted into a steady current of electrical energy.

The power is then fed into an electrical thrust system. Instead of ejecting gases, these expel charged particles, often in the form of Xenon atoms stripped of an electron, thus creating the desired exchange of momentum. Unlike in chemical rockets, this thrust can be maintained for a long time. Some trials have even produced sustained thrust lasting months at a time.

But until now, electric propulsion in space has always been limited by the power available. Solar is the usual source, and no electric engine has ever exceeded a handful of kilowatts. Nuclear reactors can lift that constraint. They can produce hundreds of kilowatts, even megawatts, and allow the true power of electric propulsion to be unleashed.

A two-hundred-kilowatt electric engine, one ten times more powerful than anything built so far, could send a twenty-ton spacecraft to Jupiter in less than five years. A megawatt reactor, one still easily within the bounds of possibility, could reduce the journey time to Mars to about twelve weeks. More powerful reactors could ship cargo to the moons of Jupiter, to Saturn, and to the very edges of the Solar System.

Ions streaming out of an electric propulsion system under test at NASA JPL. Courtesy NASA/JPL-Caltech.

Space Reactor Freedom

Before all that, NASA needs to demonstrate the concept.

The plans for Space Reactor Freedom are still vague. The details we do have, however, suggest that NASA is prioritising speed over everything else. Nuclear propulsion is not a new idea, they said at a presentation in March, but rather something that has long suffered from poor execution. Over the past six decades, the agency has launched twelve nuclear efforts, yet put nothing more than a single short-lived satellite into orbit.

Their goal is to change this. NASA wants to go fast. They have set a target of launching in 2028, and they want to follow a design based on established technology. Indeed, they think much of the development work is already done, and that the remaining challenge is more about integrating the components than building them.

At the heart of the spacecraft will be a twenty-kilowatt reactor. Details about this are sparse, but NASA boss Jared Isaacman said it was already ‘mostly built’. Yet where it is, and who built it, remain unknown to the public.

This reactor will be mounted on a module originally planned for the Gateway, a space station that was supposed to be placed around the Moon. But that station is now on pause, and the module, which is equipped with electric propulsion systems, could be integrated with a nuclear power source.

This ‘notional concept’ is about as far as NASA seems to have got.

Again, details of how this would work are limited, but assuming it can be done, NASA would then have a spacecraft capable of travelling to Mars. Onboard, the agency would put a payload of helicopters, each similar to the small Ingenuity helicopter that flew over the sands of the Red Planet a few years ago.

These helicopters would send back some interesting data, but the science is not really the point of this mission. Instead, Isaacman sees it as a way to prove nuclear technology can work in space. He hopes it would be followed by a series of more powerful missions. These will unlock the full potential of nuclear propulsion, and act, as he puts it, as the ‘transcontinental railroad of the Solar System’.

The deadline of 2028 is still ambitious. Even if the technology is already there, anything nuclear will face regulatory hurdles. The reactor will need to be safe – an accident could be fatal to the dream – and ensuring that will take time. So will the steps of making sure the design actually works. But Isaacman is still right to challenge NASA to move fast.

Indeed, the future direction of space exploration may rest on his success. If the reactor flies – whether that is in 2028 or in the early 2030s – it should inspire future missions to Mars, to Jupiter, and beyond. The road ahead is surely more challenging than NASA will admit now, but once the tech is in place and proven, then the outer Solar System awaits.

The logic of radioactive decay inverts the usual desire to remove debris from orbit as soon as possible. In such cases, it is better to leave radioactive material in space, allow it to safely decay, and only let it re-enter once the radiation has fallen to safe levels.

The Week in Space and Physics: Artemis II Returns - The Quantum Cat

2026-04-22T13:31:36.000Z

Orion’s heat shield photographed after splashdown in the Pacific Ocean. Credit: US Navy.

After travelling further into space than any human before them, the crew of Artemis II returned safely to Earth on April 10th.

Their voyage lasted ten days, and covered a distance of almost seven hundred thousand miles. At their apex, they were more than a quarter of a million miles from Earth. As they passed over the Moon, they ventured closer to our natural satellite than anyone since 1972.

The moment of greatest peril, though, came in the final minutes of their mission. Their Orion capsule, named Integrity by the crew, hit the outer atmosphere at a speed greater than twenty-four thousand miles per hour. Humans have rarely travelled this fast. Only the Apollo missions, as they too returned from the Moon, have reached similar speeds.

Before launch, some concern had been raised about the ability of the capsule’s heat shield to protect the crew from the dangers of re-entry. In Artemis I, the uncrewed first test flight, this shield did not perform as expected. Later analysis showed it had been damaged during its plunge through the atmosphere.

In an effort to avoid a repeat, NASA engineers redesigned the trajectory the capsule follows during re-entry. They also tested the heat shield on the ground – though, of course, nothing we can do in a lab is able to recreate the reality of falling through the atmosphere at thirty-five times the speed of sound.

Fortunately, the shield seems to have performed as expected. Images taken of it after splashdown appear to show it in good condition, with little of the charring and erosion seen after Artemis I. That is good news. More work, of course, is needed. NASA will now study all the data obtained - including from observation aircraft - and subject the shield to a series of tests to better understand how it behaved.

As they do this, however, attention will surely turn to Artemis III. Until recently, this mission was supposed to take humans to the lunar surface for the first time in decades. For this, NASA was relying on SpaceX to provide a lander in the form of Starship. But progress has been much slower than hoped, and Starship simply won’t be ready to support a landing in time.

Instead, Artemis III will now remain in Earth orbit. Instead of going to the Moon, astronauts will practice docking with the lander. If SpaceX can get Starship into orbit and show sufficient control for a safe approach, the Orion capsule should dock with Starship. That would prove the technical ability of both vehicles to work together. But it would also allow operators and astronauts to get experience in what promises to be a challenging operation.

NASA has also introduced a bit of competition. Blue Origin has been working on its own lunar lander, which Orion could, if the lander is launched in time, use as a docking target as well. That, if successful, would give NASA an alternative way to reach the Moon before the decade is out.

The Darkening Waves of Mars

Until the 1960s, astronomers were convinced that the surface of Mars was periodically swept by ‘waves of darkening’. These would come and go with the seasons, and would spread from the polar regions towards the equator. Nobody knew what was causing these waves, but most theories held that they were somehow linked to seasonal shifts on the red planet.

A paper from 1966 paper summarised the two most common explanations. The first, and favourite, held that the warmth of the Martian spring was melting the polar caps and putting moisture into the air. This sparked waves of plant growth, which from Earth we saw as a wave of darkness spreading around the planet.

The other, more boring suggestion argued that seasonal changes in temperature caused wind patterns to shift. These winds would at times blow clouds of dust off the surface, revealing darker underlying rocks. When winds calmed, the dust would settle and Mars would seem to become brighter again.

When spacecraft first arrived at Mars, it became clear that the first theory was utterly wrong. The Red Planet does not have plant life, and it does not show a seasonal shift in colour as vegetation grows and dies. Indeed, since the dawn of Martian exploration, we have barely noticed any kind of annual change in the colours of Mars.

Yet, over a longer scale, Mars’ surface does show some shifts in colour. Mars’ Utopia Planitia – a vast basin that may once have held a small sea – has gradually become much darker over the past few decades.

The boundary between dark and tan areas in Utopia Planitia has shifted over the past half century. Credit: ESA.

A comparison of photographs taken by NASA’s Viking orbiter in 1976 and by ESA’s Mars Express in 2024 shows this change clearly. Places that were once tan in colour are now black, and this darkness seems to be spreading.

Researchers do not know for sure why this is happening. But it is probably caused by dust blowing in Mars’ thin air. Either, ESA says, black volcanic ash is being blown by the wind and covering tan areas with darker material; or winds are blowing tan dust off previously covered areas, and so revealing the underlying darker rocks.

Voyager

After travelling for almost half a century, the Voyager 1 probe now lies more than twenty-five billion kilometres from Earth. It is the most distant man-made object in the universe, and, remarkably, it is still sending data back to us.

Voyager owes this longevity in part to the nuclear batteries that supply it with energy. These are based on a core of plutonium, and convert its radioactive decay into electrical power. But over time the plutonium is decaying, and as it does, the power generated is also decreasing. This will eventually mean the end of Voyager. Sometime in the coming years the power output will fall below the level needed to operate its radios, and contact with the probe will be lost.

Until that moment, however, operators are doing what they can to keep the spacecraft running. NASA has developed a plan for switching off Voyager’s scientific instruments one by one, a process that balances the risk of running short of power with the desire to return valuable data for as long as possible.

At the end of February, however, operators noticed a sudden drop in Voyager’s power output. Out of caution, they decided to switch off a device called the LCEP, an instrument that measures levels of charged particles around the probe.

Only two other scientific devices remain operational on Voyager 1. NASA has plans to reconfigure all of Voyager’s electrical systems sometime next year, which they hope will cut power use and extend the remaining life of the probe. It might even, NASA said, allow mission control to turn the LCEP back on.

Are Quarks Fundamental?

Until 1899, physicists thought atoms were the fundamental building blocks of nature. Their name reflects that: the word atom comes from the Greek atomos, meaning ‘indivisible’. But then J. J. Thomson discovered the electron, and the search for fundamental particles shifted to the next level down: the world of electrons, protons, and neutrons.

Later, in the 1960s, physicists realised yet another layer existed. Protons and neutrons, it turned out, were not fundamental, but were made from quarks. Today, this is where things remain: all atoms, as far as we know, are made from various arrangements of quarks and electrons.

Might there still be another level down? At the Large Hadron Collider at CERN in Switzerland, researchers have probed the structure of the quark to see if it, too, is made of some more fundamental particle.

These experiments collide protons at high speeds. In the aftermath of these impacts, the proton breaks apart into quarks. By studying how these quarks move, physicists can work out whether they act as point-like particles, or whether they have some internal structure.

In a paper published recently, researchers said these experiments have found no signs of any deeper layer of nature. Quarks appear to be point-like, or at least smaller in size than one hundred billionth of a nanometre.

Upgrades to the Large Hadron Collider should soon allow researchers to probe even smaller scales of nature. If there is another layer at the bottom, those experiments may soon spot hints of its presence.

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