Welcome back, and thanks for spending another evening here. Tonight we have fourteen stops, and many of them sit on an edge: where a belt of ice seems to end, where a black hole decides to fire, where neutron stars stop and black holes begin.
We'll meet the first star that would look green, watch a tiny comet blow a cloud bigger than the Sun, follow a wake that a small galaxy leaves in ours, see one crater slip 100 million years out of Earth's history, and ask whether the Sun once had a deadly twin. At the end, we'll ask whether matter itself lasts forever.
Get comfortable. 🌙
1. ⭐ WD J1330+6435 is the first star that would look green
Star colors follow a simple rule. Cooler stars glow orange, stars like the Sun look white, and the hottest are pale blue, like iron in a blacksmith's fire. There's no green in that list, and no one had ever credibly reported a green star.
In October 2026, Mark Hollands of the University of Warwick and his colleagues showed that white dwarfs can break the rule. The coolest of these dead stars have atmospheres about as dense as water, millions of times denser than the Sun's visible surface. Squeezed that hard, traces of carbon, calcium or sodium soak up light across a much wider range of colors than usual.
No white dwarf is close enough to see its color directly, so the team worked it out from the stars' spectra, using a model of human color vision. Most came out white. But WD J1330+6435, at about 4,000 degrees Celsius, has swallowed rocky debris from its own planetary system. The sodium in that debris absorbs the orange part of its light, leaving what Hollands called "a ghostly green glow."
The survey turned up pink and purple carbon-rich white dwarfs too, and one salmon-pink star that may be the reddest ever recorded. In the sample of white dwarfs nearest to us, about one in thirty has an unusual color.
The first green star owes its color to the planets it once had.
2. ☄️ Comet Holmes grew bigger than the Sun
In late October 2007, a small comet named 17P/Holmes, only about 3.5 kilometers across, brightened by a million times in less than a day. It was the largest outburst ever seen from a comet.
The comet had blasted out an enormous cloud of dust and gas, and it kept growing. By mid-November, the cloud was more than 1.4 million kilometers wide, bigger than the Sun itself. It was so thin that stars shone straight through it, including the bright star Mirfak as the comet drifted through Perseus.
Rachel Stevenson, Jan Kleyna and David Jewitt watched the aftermath with the Canada-France-Hawaii Telescope. Using a filter that sharpens faint details, they found fragments racing away from the nucleus at up to 125 meters per second. The pieces were too bright to be bare rocks. They were more like mini-comets, each shedding its own dust as its ice turned to gas.
Nobody knows for sure what set it off. One idea is that pressure built up as ice under the surface turned to gas, until part of the surface broke away. Remarkably, the solid nucleus survived and carried on around its six-year orbit, seemingly unbothered.
For a few weeks, a comet the size of a small town wore a cloak bigger than the Sun.
3. 🌀 Black holes of every size switch on their jets at the same moment
Black holes come in very different sizes. Some weigh about ten Suns, and others millions or billions. Yet in 2026, Adelle Goodwin of Curtin University and Andrew Mummery of the Institute for Advanced Study found that they seem to follow the same rule for when to fire jets.
The clue came from tidal disruption events, when a giant black hole tears apart a star that strays too close. Some of these launch a jet almost at once. Others stay quiet for months or years, then suddenly erupt in radio waves. Why the delay?
The pair studied ten well-observed events. Early on, while the black hole gorges, it can launch an outflow. But the late jets appeared when the feeding rate fell to about 2% of the Eddington limit, the point where the light from infalling gas pushes outward as hard as gravity pulls in. Black holes ten times the Sun's mass, inside our own galaxy, are already known to change their behavior at that same 2%.
The idea came together over a conversation in a bar in Madrid, at a conference. If it holds, astronomers can predict when a black hole will erupt and point their radio telescopes at the right moment.
"The physics does not seem to care how big they are," Goodwin said.
A black hole a million times heavier still keeps the same rhythm.
4. 🪐 GW Orionis is tearing its planet-forming disk apart
In our Solar System, the planets all circle the Sun in nearly the same flat plane, because they formed from one flat disk. Around stars with siblings, things can get messier.
GW Orionis is a young system with three stars. Two orbit each other about as far apart as Earth and the Sun, and the third circles them at about eight times that distance. Around them all lies a huge disk of gas and dust where planets may be forming.
Using ALMA, two teams found that the disk is broken into three rings, about 46, 185 and 340 times the Earth-Sun distance from the center, tilted in different directions. The outermost is the largest ring ever seen in a planet-forming disk. The inner one is badly tilted, and the Very Large Telescope caught the shadow it casts across the disk beyond.
Stefan Kraus of the University of Exeter and his team tracked the three stars for more than 11 years and found that their orbits don't line up with each other or with the disk. Their simulations suggest the stars' uneven pull is ripping the disk into rings. Jiaqing Bi's team thinks the stars alone can't do it, and that a planet hidden between the rings is also needed.
Some planets may be born in disks that their own suns are tearing apart.
5. 🌌 The Large Magellanic Cloud leaves a wake in the Milky Way
The Large Magellanic Cloud is the larger of two small galaxies that orbit our own. It's about 160,000 light-years away, with less than a quarter of the Milky Way's mass.
In 2021, a team led by Charlie Conroy at the Center for Astrophysics | Harvard & Smithsonian used data from ESA's Gaia and NASA's NEOWISE spacecraft to map more than 1,300 stars in the Milky Way's faint outer halo. They found the Large Magellanic Cloud sailing through the halo like a ship through water, leaving a wake of stars behind it, 200,000 to 325,000 light-years from the center of our galaxy.
The stars are only the visible part. The halo should be filled with dark matter, and the wake in the stars is thought to trace a wake in that invisible material, the stars riding on it "like leaves on the surface of this invisible ocean."
That dark matter also drags on the little galaxy and slows it down. Its orbit will keep shrinking until it collides with the Milky Way in about 2 billion years.
The wake might even help test what dark matter is. "You can imagine that the wake behind a boat will be different if the boat is sailing through water or through honey," Conroy said.
Our galaxy's companion is stirring up something we can't see, and the stars are showing us the ripples.
6. 🌍 An Oklahoma crater just slipped out of Earth's ring story
In 2024, Andy Tomkins of Monash University and his colleagues proposed something startling: about 466 million years ago, Earth may have had a ring.
Their evidence was a burst of impacts in the Ordovician period. They mapped 21 craters from that time onto where the continents sat back then, and every one fell within 30 degrees of the equator, even though only about 30% of the land able to preserve them was there. That's like tossing a three-sided coin and getting the same side 21 times. Their explanation is an asteroid that strayed too close, was torn apart by Earth's gravity, and formed a ring whose debris rained down over millions of years.
The idea depends on knowing when each crater formed. In 2026, Elizabeth Catlos's team at the University of Texas at Austin dated tiny zircon crystals from the buried crater beneath Ames, Oklahoma, long counted among North America's Ordovician impacts. It's about 370 million years old, nearly 100 million years younger than thought. Its old age came from fossil teeth that were probably already ancient when the impact churned them up.
The new date puts the impact close to a great mass extinction about 372 million years ago. The ring idea rests on many craters, not one, but this one no longer belongs to that ancient bombardment. "We're basically taking a major pawn out of the Ordovician Meteor Event," Catlos said.
Every crater keeps a date, and history depends on reading it right.
7. ⭐ ZTF SLRN-2020 swallowed a planet that spiraled in
In May 2020, Kishalay De of MIT was searching sky-survey data for pairs of stars in eruption when he noticed a star about 12,000 light-years away, near the constellation Aquila, that brightened a hundredfold in about a week. "It was unlike any stellar outburst I had seen in my life," he said.
Over the following year, the star glowed brightly in infrared light, as gas it threw off cooled into dust. Yet the total energy released was only about a thousandth of any merger of two stars ever seen. A companion a thousandth of the Sun's mass is about the mass of Jupiter. This was a planet, crashing into its star, the first ever caught in the act.
The 2023 study assumed the star was aging into a red giant and had swollen up to engulf its planet, the fate expected for Earth in billions of years. Then Webb took a closer look. In 2025, a team led by Ryan Lau of NSF NOIRLab found that the star is too faint to be a red giant. It never swelled at all.
Instead, the planet's orbit, already closer than Mercury's, shrank over millions of years until it grazed the star's atmosphere, and then it fell in fast.
The star didn't reach out for its planet. The planet spiraled in.
8. 🕳️ GW190814 found something in the mass gap
For decades, astronomers noticed a strange gap. The heaviest known neutron stars weighed no more than about 2.5 Suns. The lightest known black holes weighed about 5. Nothing seemed to live in between.
On August 14, 2019, the LIGO and Virgo detectors caught gravitational waves from a black hole of 23 Suns merging with a mystery object of 2.6 Suns, squarely in the gap. The collision happened about 800 million light-years away.
Was it the heaviest neutron star ever found, or the lightest black hole? Nobody could say. Dozens of telescopes searched for a flash of light that might have revealed a neutron star being torn apart, and saw nothing. That doesn't settle it, though. The event was far away, and a black hole nine times heavier could have swallowed a neutron star whole, without spilling any light.
The partners' masses differed by a factor of nine, the most lopsided pair yet seen in gravitational waves, and that's hard for current models to make.
"The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities," said Patrick Brady, then the LIGO Scientific Collaboration's spokesperson.
Nature may not draw a clean line between neutron stars and black holes.
9. 🧊 The Kuiper Belt has a cliff, and maybe something beyond it
Beyond Neptune lies the Kuiper Belt, a ring of icy bodies that includes Pluto. Count its members going outward, and something odd happens: at around 50 times the Earth-Sun distance, their numbers drop off sharply. Astronomers call it the Kuiper cliff.
That's surprisingly compact. Disks around other young stars typically stretch about twice as far. Either the Sun was born with an unusually small disk, or something trimmed its edge, perhaps an undiscovered planet, perhaps leaving a second belt farther out.
NASA's New Horizons spacecraft, which flew past Pluto in 2015, has been sampling that frontier. Its dust counter, built by students at the University of Colorado Boulder, kept detecting more dust than expected as the spacecraft traveled from 45 to 55 times the Earth-Sun distance, where models said it should be thinning. Much of that dust comes from collisions between icy bodies, so there may be more of them out there than anyone expected.
Meanwhile, Fumi Yoshida's team reanalyzed Subaru Telescope images taken for New Horizons with software designed to spot near-Earth asteroids and space debris. They found two objects orbiting beyond the cliff. New evidence suggests the belt may reach 80 times the Earth-Sun distance or farther.
The Solar System's edge might be a doorstep, not a wall.
10. 🌌 XLSSC 122 is a cluster that grew up too fast
Great clusters of galaxies are supposed to take a long time to build, gathering smaller groups one by one. XLSSC 122 didn't wait.
We see it as it was about 10 billion years ago, during "cosmic noon," when the universe was making stars fastest. Even then, it already looked mature. In 2026, Kyle Finner of Caltech's IPAC and his colleagues reported that Webb had caught it bending the light of galaxies behind it into arcs. That makes it the most distant cluster known to act as a strong gravitational lens.
Lensing gives a way to weigh what can't be seen. Most of the cluster's mass is dark matter, and the arcs show that an unusually large amount of it is packed into the center. "It has a mass concentration that doesn't agree with our cosmological model predictions," Finner said.
Webb also caught the cluster still assembling, with galaxies continuing to merge. It found the earliest known glow from stars drifting between the galaxies, stars knocked loose in those collisions. Near the center, that faint light follows the dark matter closely.
The team now hopes to study dozens more early clusters to see whether XLSSC 122 is a rare oddity or a sign that the universe built its giants faster than expected.
Ten billion years ago, a giant had already moved into its adult shape.
11. 🪐 WASP-17b isn't round where the wind blows
Exoplanets are usually drawn as neat circles. But WASP-17b, a giant planet about 1,300 light-years away, turns out to be lopsided.
WASP-17b is a "hot Jupiter," a gas giant so close to its star that one side always faces it, while the other stays in permanent night. When the planet passes in front of its star, a little starlight filters through the thin rim of its atmosphere on the way to us.
Usually, astronomers average that rim into a single ring. In 2026, a team led by Lili Alderson of Cornell University used a technique called "transmission strings," developed by David Grant and Hannah Wakeford at the University of Bristol, to read different parts of the rim separately in Webb's data. "We've gone from a ring to understanding where on the ring the gemstones are, so to speak," Alderson said.
The atmosphere bulges outward on the planet's "evening" edge, near the equator. Powerful winds carry hot gas from the dayside around to the night, puffing up that side, while the "morning" edge, where cooled gas returns, sits lower.
It's exactly what theory predicted, now seen for real. "This is proof of concept that planets are in fact 3D objects," Alderson said.
Even seen from 1,300 light-years away, a planet's weather can change its shape.
12. 🌑 Nemesis was a deadly twin the Sun probably never had
In 1984, a 26-million-year rhythm had recently been reported in the fossil record: mass extinctions seemed to come on a schedule. Marc Davis, Piet Hut and Richard Muller offered an extraordinary explanation.
Perhaps the Sun has an unseen companion star on a long, stretched orbit. Each time it swings closest, it would plow through the Oort Cloud, the vast shell of comets around the Solar System, and send over a billion of them falling inward. Several would hit Earth over the next million years. The star, they calculated, would now be near its farthest point, about 2.4 light-years away, and "will present no danger to the Earth until approximately AD 15,000,000."
The star picked up a fitting nickname, Nemesis, and astronomers went looking for it. NASA's WISE spacecraft scanned the whole sky in infrared in 2010 and 2011. In 2014, Kevin Luhman of Penn State reported that no object the size of Saturn or larger lurks out to 10,000 times the Earth-Sun distance, and nothing bigger than Jupiter out to 26,000. "The outer solar system probably does not contain a large gas giant planet, or a small, companion star," he said. Theories of periodic extinctions caused by such a body had largely been ruled out even before WISE.
As far as we can tell, the Sun has no dark twin.
13. ✨ Dark stars may have shone on dark matter
Every star we know shines by fusion, atoms crushed together in its core. But in 2008, Katherine Freese, Doug Spolyar and Paolo Gondolo proposed that some of the very first stars may have worked differently.
If dark matter is made of particles that destroy each other when they collide, then in the dense clumps where the first stars formed, those collisions could heat a collapsing cloud of hydrogen and helium from inside. The result would be a dark star: huge, bright, yet puffy, held up by a tiny amount of dark matter rather than fusion. Some might grow to a million times the Sun's mass and later collapse into giant black holes.
Freese and her colleagues think Webb may have spotted some. In 2025, a study led by Cosmin Ilie of Colgate University found that four of the most distant objects known, including JADES-GS-z14-0, seen less than 300 million years after the Big Bang, fit the dark-star picture. In one, the team saw a hint of a telltale absorption line, though the signal is noisy.
Other astronomers read the same object very differently. Two teams using ALMA detected oxygen in JADES-GS-z14-0, an element made by generations of ordinary stars, and described it as a galaxy maturing astonishingly fast.
Dark stars remain a beautiful idea, still waiting for proof.
14. ⚛️ Even protons may not last forever
Every atom has protons at its heart, and as far as anyone has seen, they never fall apart. But many grand unified theories, attempts to merge the forces of nature into one, predict that the proton is unstable, with a finite but extraordinarily long lifetime.
Physicists have gone looking. Japan's Super-Kamiokande experiment watched tens of thousands of tonnes of ultra-pure water from 1996 to 2018, waiting for the flash of a single proton breaking apart in one of the favorite ways theory predicts. It saw none. So, if protons decay that way, they must last on average more than 24 billion trillion trillion years, over a trillion trillion times the age of the universe. The search goes on with larger detectors, such as Hyper-Kamiokande.
Why care about something so slow? Because in the very far future, it could decide everything. In 1997, Fred Adams and Gregory Laughlin traced what would happen if protons do decay. Long after the last stars burn out, the dead white dwarfs and neutron stars left behind would slowly dissolve as their protons decay. For a typical decay rate in those theories, a white dwarf powered only by proton decay would give off about 400 watts, enough to light a few light bulbs.
If protons decay, even the solid stuff of the universe is only passing through.
🌙 One last thought before you sleep
Tonight was full of edges.
The edge of the Kuiper Belt, which may not be an edge at all. The gap between neutron stars and black holes, which may not be a gap. The 2% line at which a black hole of any size lets loose its jets. The rim of a planet's atmosphere, bulging in the wind.
Some boundaries turned out to be firmer than we thought, like the empty space where Nemesis was supposed to be. Others turned out softer. A crater slipped 100 million years. A star swallowed a planet, but not the way anyone pictured.
And beyond all of them sits the last boundary we know of: the question of whether matter itself endures. Even protons, the steady heart of every atom, may one day let go.
Edges are where the universe tells us the most, because that's where our certainty runs out.
That's all for tonight. Thanks for wondering along with me. Good night, and clear skies. 🌌
— Kasi