Welcome back, and thanks for spending another evening here. Tonight we have sixteen stops, and many of them are about things hiding in plain sight: inside planets, behind starlight, and in the quiet background of the sky.
We'll watch a star in Andromeda that explodes every year, meet the youngest planet ever found, dig for the remains of a lost world buried inside our own, trace a spiral at the edge of the Solar System that nobody has seen, and find a galaxy known only by four lonely star clusters. At the end, we'll ask whether empty space itself is as permanent as it looks.
Get comfortable. 🌙
1. ⭐ M31N 2008-12a is a star that explodes every year
A nova happens when a white dwarf, the dense leftover core of a star, steals hydrogen from a companion. The stolen gas piles up on its surface until it ignites in a runaway nuclear blast, briefly shining up to a million times brighter than the Sun. Most novae take decades or longer to build up to another blast.
M31N 2008-12a, in the Andromeda Galaxy, erupts about once a year, and possibly every six months. Its white dwarf weighs about 1.38 times the Sun, right up against the 1.4 limit a white dwarf can reach, and it gorges on the wind of a red giant companion.
Each blast throws gas outward at up to 10,000 kilometers per second, sweeping up the thin gas around it. Over countless eruptions, that has carved an enormous cavity. In 2019, astronomers found that the nova sits inside a glowing "super-remnant" at least 440 by 290 light-years across, larger than almost every known remnant of a supernova. To build something that big, it must have been erupting like this for millions of years.
And it's still gaining weight. Within a million years, the white dwarf may cross its limit, making it a leading candidate to end as a type Ia supernova.
A star that has been clearing its throat for millions of years may be working up to one final shout.
2. 🪐 Elias 2-24 b is the youngest planet ever found
Most of the 6,000 or so known exoplanets are billions of years old. Baby planets are hard to spot, because they're buried in the dusty disks they're forming from.
About a decade ago, the ALMA radio telescope in Chile saw a gap in the disk around the young star Elias 2-24, about 450 light-years away. Gaps like that are thought to be carved by growing planets. Then the Very Large Telescope spotted a faint dot sitting in the gap. Was it a planet, or a smudge?
In September 2026, a team led by Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, found the same dot in archived Keck Observatory images from 2018 and 2020. It moved like a planet, confirming Elias 2-24 b: a world about as massive as Jupiter and less than a million years old.
That's a problem for theory. Models say a Jupiter takes about 5 million years to form at Jupiter's distance from the Sun, and longer farther out. Elias 2-24 b sits 55 times farther from its star than Earth is from the Sun. The previous record holders were all more than 5 million years old.
A giant planet has grown up faster than our best models allow.
3. 🌍 Pieces of Theia may be buried inside Earth
Early in the Solar System's history, a Mars-sized world called Theia is thought to have slammed into the young Earth. Debris from the crash came together to form the Moon. But where did Theia itself go? No trace of it has turned up in the asteroid belt or in meteorites.
Meanwhile, deep inside Earth, geophysicists have known since the 1980s about two strange blobs of rock sitting on top of the core, one beneath Africa and one beneath the Pacific. Each is about twice the size of the Moon. Earthquake waves slow down as they pass through them, which suggests the blobs are denser and richer in iron than the rock around them.
In 2019, Caltech geophysicist Qian Yuan was listening to a talk about the Moon's origin when the speaker mentioned that nobody knows where Theia ended up. "I had a 'eureka moment'," Yuan said. Maybe the blobs are Theia.
The team's simulations showed it could work. Most of the impact's energy stayed in Earth's upper mantle, so the lower mantle didn't fully melt. Chunks of Theia's iron-rich rock sank intact to the bottom, like wax in a lava lamp that's been switched off.
It's still a hypothesis. But the lost world may never have left. It may be under our feet.
4. 🕳️ Abell2744-QSO1 is a black hole that came before its galaxy
Which comes first, the galaxy or its giant black hole? The usual story is that galaxies come first. Their biggest stars collapse into black holes, which then feed and merge and grow. But Webb keeps finding giant black holes that seem to have had no time to grow that way.
Abell2744-QSO1 is one of the "little red dots," compact objects Webb has found in the early universe. We see it as it was 700 million years after the Big Bang, magnified and copied three times by the gravity of a foreground galaxy cluster. It's only about 1,300 light-years across.
In May 2026, a team used Webb to map how the gas inside it moves. The gas circles the center the way planets circle the Sun, which happens only when nearly all the mass sits at the middle. That let them weigh the black hole directly for the first time this early in cosmic history: about 50 million Suns, roughly two-thirds of everything in QSO1. In nearby galaxies, the black hole is a tiny fraction of the total.
The gas is also almost pure hydrogen and helium, with heavier elements at less than 0.5% of the Sun's level. A galaxy full of stars would have polluted it long ago.
The team thinks the black hole was born big, perhaps from a collapsing gas cloud, or even in the first second after the Big Bang. "It's a paradigm shift," said Roberto Maiolino. Here, the black hole seems to have come first, and the galaxy is still catching up.
5. 💥 iPTF14hls is a supernova that wouldn't stop
Supernovae are supposed to be final. A star explodes, shines brightly for about 100 days and fades away. Thousands have been seen, and that's what they all do.
When the Palomar Transient Factory found iPTF14hls in September 2014, it looked ordinary. Then, months later, astronomers at Las Cumbres Observatory noticed it was getting brighter again. Over the following years, it brightened and dimmed at least five times. It stayed bright for more than 600 days, and the gas in its spectrum hardly slowed down, as if the explosion wasn't thinning out.
Then the team checked old photographs and found something stranger: a possible eruption at the same spot in 1954.
The star was probably at least 50 times the Sun's mass. One idea is that a giant star's core got so hot that it began turning energy into matter and antimatter, which triggered blasts that threw off its outer layers again and again before the end. But the energy iPTF14hls released is more than that model can explain. "This supernova breaks everything we thought we knew about how they work," said Iair Arcavi, who led the study.
Some stars, it seems, die more than once.
6. ☄️ The Oort Cloud may hide a spiral
Far beyond Neptune, the Solar System is thought to be wrapped in the Oort Cloud, a vast swarm of icy bodies reaching perhaps 100,000 times Earth's distance from the Sun. Nobody has ever seen it directly. We know it's there because of the long-period comets that fall in from it.
In 2025, David Nesvorný of the Southwest Research Institute and colleagues looked closely at their computer simulations of how the Oort Cloud formed. In its inner part, they found a surprise: the icy bodies are arranged in a slightly warped disk about 15,000 times Earth's distance from the Sun across, tilted about 30 degrees to the planets' orbits. Seen from far away, it would look like a spiral with two twisted arms.
The sculptor is the Milky Way itself. The gentle, steady pull of our galaxy's stars and gas, called the Galactic tide, slowly twists the orbits of these distant objects. The spiral showed up in every simulation that included the tide, no matter which passing stars were added. It forms within a few hundred million years of the Solar System's birth and lasts for billions.
The team admits its chances of being seen are feeble. The objects that trace it are small, faint and very far away.
Our Solar System may wear a tiny spiral galaxy around its edges, and we may never see it.
7. 🌌 CDG-2 is a galaxy found only by its star clusters
Some galaxies are so faint they're nearly invisible. How do you find a galaxy you can't see?
David Li of the University of Toronto and his team tried looking for its companions instead. Globular clusters are tight, ancient balls of stars that usually orbit galaxies. They're bright and tough, hard for gravity to pull apart. So the team searched for tight groups of globular clusters with no obvious galaxy around them.
One group, four clusters in the Perseus galaxy cluster about 300 million light-years away, became Candidate Dark Galaxy-2, or CDG-2. Follow-up images from Hubble, ESA's Euclid telescope and the Subaru Telescope revealed a faint glow around the four clusters: a galaxy after all. "This is the first galaxy detected solely through its globular cluster population," Li said.
CDG-2 shines with the light of only about a million Suns, and its four clusters make up 16% of that light. The Milky Way, by comparison, has more than 150 globular clusters. By the team's estimate, 99% of CDG-2's mass is dark matter. Its gas was probably stripped away by encounters with other galaxies in the crowded cluster, leaving almost nothing to make new stars.
Four star clusters were the lanterns marking a galaxy made almost entirely of darkness.
8. ⭐ V1309 Scorpii was two stars becoming one
Astronomers had long suspected that some pairs of stars, orbiting so close that they touch, eventually merge. A famous forecast that one such pair would soon merge didn't hold up. But a merger had already been caught, almost by accident.
In September 2008, a new star blazed up in Scorpius. It was named V1309 Scorpii, and its outburst resembled the strange eruption of V838 Monocerotis.
Luckily, a survey called OGLE had been photographing that patch of sky since 2001. When astronomers went back through the records, they found that the star had been two stars all along, a touching pair orbiting each other every 1.4 days or so.
The records showed the pair's orbit getting faster year after year as the two stars spiraled together. The light curve changed shape too. In March 2008, half a year before the outburst was noticed, the system began to brighten steadily. Then the two stars became one.
It was the first direct proof that touching stars really do end up merging, and it showed that mergers can make outbursts like this one.
For seven years, a survey watched two stars fall into each other without knowing it was watching.
9. 🪐 Jupiter's core is fuzzy, and nobody agrees why
The textbook picture of Jupiter starts with a dense core of rock and ice, which then gathered a huge envelope of gas. You'd expect that core to have a clear edge.
But NASA's Juno spacecraft, by measuring Jupiter's gravity in fine detail, found a core that seems less dense and more spread out than expected, its heavy material mixed partway up into the gas above. "It suggests that something happened that stirred up the core," said Andrea Isella of Rice University.
In 2019, Isella and Shang-Fei Liu proposed something dramatic: a head-on collision, about 4.5 billion years ago, with a young planet about 10 times Earth's mass. The impactor would have plunged through the atmosphere "like a bullet" and splattered the core outward. It could take billions of years for the material to settle again.
But in 2025, another team rejected the idea. Their simulations found that head-on hits would be rare, and that even a direct hit can't make Jupiter's fuzzy core. They think the fuzziness is simply how Jupiter was built.
Either way, the largest planet in the Solar System doesn't have the neat heart we drew for it. Even Jupiter's center is a mystery.
10. 🧲 HESS J1731-347 holds a neutron star that's too light
When a big star's core collapses in a supernova, it can leave behind a neutron star, an object about as heavy as the Sun crushed into a ball the size of a city. Neutron stars are usually around one and a half times the Sun's mass.
At the center of a supernova remnant called HESS J1731-347, though, there's one with only about half the mass of a typical neutron star.
A team at the University of Tübingen worked out its weight from the X-rays glowing off its hot surface. The key was a nearby companion star whose distance ESA's Gaia mission measured precisely. They found a mass of about 0.77 times the Sun, packed into a radius of about 10.4 kilometers.
That leaves two possibilities. It may be the lightest neutron star known, and nobody's sure how a supernova could make one so light. Or it may be something even stranger: a strange star, made of a form of matter in which the particles inside protons and neutrons, called quarks, roam free. "This is currently the most promising quark or strange-matter star candidate we know of so far," said Andrea Santangelo, though he added that its properties also fit an ordinary neutron star.
A dead star small enough to be strange may be holding matter we've never seen.
11. 🟤 IC 348 is making brown dwarfs only twice Jupiter's mass
Stars are born when clouds of gas collapse. The smallest true stars are about 8% of the Sun's mass. Below that are brown dwarfs, which form the same way but never get hot enough inside to fuse hydrogen. So how small can a collapsing cloud go and still make something?
To find out, astronomers pointed Webb at IC 348, a young star-forming region about 1,000 light-years away in Perseus. In 2022, they found brown dwarfs only three to four times Jupiter's mass. In September 2026, they went deeper and found brown dwarfs only twice the mass of Jupiter, just 0.19% of the Sun's mass. They're the lightest brown dwarfs known, and models of star formation have trouble explaining them.
There were more surprises. One of the lightest seems to have a disk around it, so it might be building planets of its own, even though it's no heavier than a planet itself. And the spectra of the smallest showed signs of hydrocarbons, molecules of hydrogen and carbon seen only in the lowest-mass brown dwarfs. They might deserve a class of their own.
Star formation can make objects so small that the line between a star's little sibling and a planet blurs away.
12. 💥 GRB 211211A was the wrong kind of explosion
Gamma-ray bursts are the most powerful explosions in the universe, and they come in two kinds. Long bursts, lasting from a couple of seconds to about a minute, come from massive stars collapsing as supernovae. Short ones, under two seconds, come from collisions of neutron stars, which leave behind a glowing cloud called a kilonova. Or so astronomers thought.
In December 2021, NASA's Swift and Fermi telescopes caught a long burst, GRB 211211A, only about a billion light-years away, unusually close. Jillian Rastinejad, then a PhD student at Northwestern University, was drawn to it partly because its gamma rays looked like those of an earlier long burst that had never produced a supernova.
Using the Gemini North telescope, her team found a glow at that spot that was bright in the near-infrared but faint in visible light. That's the signature of a kilonova: heavy elements made in a neutron-star collision block visible light but let infrared through. A second team, led by Eleonora Troja, reached the same conclusion independently.
So a long burst came from a merger, not a dying star. Duration alone, it turns out, doesn't tell you what exploded.
The universe's most powerful explosions don't always follow the rules we wrote for them.
13. 🪐 Neptune's clouds vanished when the Sun went quiet
Neptune usually wears bright white clouds, high in its blue atmosphere. But around 2019, they began to disappear. "We essentially saw cloud activity drop within a few months," said Imke de Pater of UC Berkeley. By 2020, the planet looked almost bare, except over its south pole.
Erandi Chavez, then an undergraduate at Berkeley, led a study of nearly 30 years of images from Hubble, the Keck Observatory and Lick Observatory. Neptune's clouds didn't follow its seasons, which last about 40 years each. Instead, they followed the Sun's 11-year cycle of activity. About two years after the Sun reached its stormy peak, Neptune grew more clouds.
That's startling, because Neptune is so far away that it receives sunlight at about 0.1% of the intensity Earth does. The team's idea is that the extra ultraviolet light at solar maximum sets off chemical reactions high in Neptune's atmosphere, and after a couple of years, the products make clouds.
As of June 2023, the clouds still hadn't come back to their old levels.
From the far edge of the planets, Neptune may still be taking its weather cues from the Sun.
14. 📡 ARCADE 2 found a radio roar nobody can explain
In July 2006, a NASA balloon carried an instrument called ARCADE 2 about 37 kilometers up from Palestine, Texas. Its receivers sat in more than 500 gallons of liquid helium, chilled to 2.7 degrees above absolute zero, the same temperature as the afterglow of the Big Bang, so the instrument's own heat couldn't spoil the measurement.
It was looking for faint warmth from the universe's first stars. Instead it found radio noise six times louder than predicted. "The universe really threw us a curve," said Alan Kogut, who led the team.
The obvious suspects were radio galaxies, which fill the sky with a background hiss. But there don't seem to be nearly enough. "You'd have to pack them into the universe like sardines," said Dale Fixsen. The team also ruled out the first stars and gas around our own galaxy.
More than a decade later, the mystery hasn't gone away. A 2022 workshop concluded that the radio background still seems several times brighter than known sources can explain, making it the least understood glow of any kind in the sky.
Something out there is humming, and we still don't know what it is.
15. ☄️ Apophis will pass closer than our satellites in 2029
When asteroid Apophis was discovered in 2004, early calculations suggested it might hit Earth in 2029, 2036 or 2068. It's about 340 meters across on average, and at least 450 meters along its longest side. Years of telescope and radar tracking have since ruled out any impact for at least 100 years.
But on April 13, 2029, it will come astonishingly close: about 32,000 kilometers above Earth's surface. That's closer than the satellites in geostationary orbit, about 36,000 kilometers up. Observers in the Eastern Hemisphere should be able to see it with their own eyes, no telescope needed.
NASA says an asteroid this big passes this close only once every few thousand years on average, so it has probably never happened in recorded history.
The flyby is a natural experiment. Earth's gravity will pull, twist, stretch and squeeze Apophis, changing its orbit and probably its spin, and maybe setting off small landslides on its slopes. By watching how it responds, scientists can work out what it's made of inside. NASA's OSIRIS-APEX spacecraft and ESA's Ramses mission will be there to watch.
Once feared as a threat, Apophis is coming instead as a guest.
16. 🌌 Empty space may not be permanent
Even perfectly empty space isn't truly empty. It's filled with the Higgs field, which gives particles their mass. The field has a resting value, like a boulder resting at the bottom of a valley, and that value sets the masses of electrons and quarks, and so the rules that let atoms exist.
But there might be a deeper valley farther out. If so, our empty space is only a "false vacuum." Through quantum tunneling, a tiny patch of the universe could, by pure chance, slip into the deeper valley. If the patch were big enough, it would grow into a bubble expanding at nearly the speed of light, and inside it the laws of physics would change, making matter as we know it impossible.
For decades this was pure speculation. Then, in 2012, CERN's Large Hadron Collider found the Higgs boson, and its mass let physicists actually calculate the odds. In 2018, a Harvard team produced the first complete estimate: if the known laws of particle physics are the whole story, our vacuum should last about a 1 followed by 139 zeros years. The universe is only about 14 billion years old.
There are big caveats. New physics could change the answer completely, and current measurements can't rule out that our vacuum is perfectly stable.
Even the emptiness of space may be resting only for now, in a valley that has held for a very, very long time.
🌙 One last thought before you sleep
So much of tonight was about what hides inside the familiar.
A lost world may sit under our feet. A spiral may wrap the Solar System. A galaxy hid behind four star clusters, and a merger hid in years of old survey photographs. Even Jupiter's heart turned out not to be where we drew it.
Again and again, the universe holds more than it shows. We learn about it slowly, by looking twice: going back through old records, measuring a gravity field a little more precisely, waiting for a dot in the dark to move.
And underneath all of it is the quiet stage everything stands on, the vacuum itself, which may be calmer and more patient than anything else we know.
The universe is full of hidden things. Some of them are holding everything else up.
That's all for tonight. Thanks for wondering along with me. Good night, and clear skies. 🌌
— Kasi