Welcome back, and thanks for spending another evening here. Tonight we have fifteen stops, and many of them are about memory: things in the universe that remember, and one thing that will one day forget.
We'll meet a planet that should have been swallowed by its star, read an ancient solar storm in the rings of trees, find a dying star making dust right beside our galaxy's black hole, climb what may be ice volcanoes on Pluto, and listen to two giant black holes keeping time like a metronome. At the end, we'll visit astronomers in the far future who may never learn that there was a Big Bang.
Get comfortable. 🌙
1. 🪐 Halla is a planet that should have been swallowed
When a star like the Sun runs low on fuel, it swells into a red giant and swallows its closest planets. So Halla, a giant planet circling the star Baekdu (also called 8 Ursae Minoris), about 530 light-years away, shouldn't be there.
Korean astronomers found Halla in 2015 by the wobble it causes in its star. It orbits every 93 days, at less than half of Earth's distance from the Sun. Then Marc Hon's team at the University of Hawaiʻi used NASA's TESS telescope to listen to the star's vibrations, which reveal what's going on deep inside. Baekdu is already burning helium in its core. That means it has already been through its giant phase, swelling to about one and a half times the size of Halla's orbit before shrinking back.
Yet the planet still follows a steady, nearly circular path. Hon called it "an extraordinary survivor."
How did it survive? One idea is that Baekdu was once two stars that merged, and the merger stopped either one from swelling large enough to reach the planet. Another is that Halla is new, built from debris thrown out by that collision.
Either it dodged the end of the world, or it was born after it.
2. ☀️ Trees remember a solar storm from the year 774
Every year a tree adds a ring, and every ring holds a little carbon-14, a form of carbon made when particles from space strike the upper atmosphere. Trees breathe it in, so their rings keep a year-by-year diary of what's been hitting Earth.
In 2012, researchers measured the rings of old Japanese cedars, one or two years at a time. Between 774 and 775 CE, the carbon-14 jumped by about 20 times more than the Sun's ordinary ups and downs could explain. A second, smaller spike turned up around 993. These sudden jumps are now known as Miyake events.
What caused them? Ice cores from the Arctic and Antarctica hold other atoms made the same way, and in 2015 they pointed to extreme bursts of particles from the Sun. The 774 storm was at least five times stronger than any solar storm our instruments have ever recorded.
The spikes have become precise clocks. In 2021, researchers used the 993 spike to date wood from the Viking site at L'Anse aux Meadows in Newfoundland, and showed that Europeans were in the Americas in 1021.
A storm on the Sun left a timestamp in the forests of Earth.
3. ⭐ IRS 3 is making dust next door to a black hole
The center of the Milky Way is a harsh place. Our galaxy's giant black hole, Sagittarius A*, sits surrounded by fierce radiation, crowded stars and fast-moving gas. You might expect anything delicate to be destroyed there.
But a dying star called IRS 3, just 0.55 light-years from the black hole, is quietly making dust. For comparison, the nearest star to the Sun is more than seven times farther from us.
IRS 3 is near the end of its life, in a stage where a star swells, cools and blows its outer layers away in powerful winds. Webb's mid-infrared instrument split its light into a spectrum and found clear signs of silicate dust, made of silicon and oxygen, which showed it's an oxygen-rich star, not the carbon-rich one some had suspected. It also found water, the first clear detection around this star.
The dust lies in layered shells reaching about 10,000 times Earth's distance from the Sun, cooling from about 930 °C near the star to about −173 °C at the edge. The star is about six times the Sun's mass and roughly 72 million years old.
"Dust production remains remarkably resilient," said Florian Peißker of the University of Cologne. Even beside a black hole, stars keep making the raw material for new worlds.
4. 🌌 LKH was the Milky Way's first big meal
The Milky Way grew by swallowing smaller galaxies. Astronomers already knew of a big one about 10 billion years ago, called Gaia-Sausage-Enceladus. Now Hubble has found an even earlier one.
The clues are globular clusters, tight balls of ancient stars that act like time capsules. Davide Massari's team measured the ages and chemistry of 39 clusters near the center of our galaxy, and combined them with measurements from ESA's Gaia mission. They expected two groups: clusters born in the Milky Way, and clusters stolen from Gaia-Sausage-Enceladus.
They found a third. These clusters are older than the stolen ones, but younger than the home-grown ones, whatever their chemistry. They must have come from a dwarf galaxy that merged with ours about 11.8 billion years ago, just 2 billion years after the Big Bang. That pushes our galaxy's known history back 1.8 billion years.
The dwarf held about 500 million Suns' worth of stars, a big share of the Milky Way's mass at the time. The team named it LKH, short for Low-energy-Kraken-Heracles, after three earlier studies that had argued for it.
"Our home is the Milky Way galaxy, but we do not know how our house was built," Massari said. Now we know where some of the first bricks came from.
5. 🌋 Wright Mons may be an ice volcano on Pluto
When New Horizons flew past Pluto in 2015, it found a patch of ground southwest of the great nitrogen-ice plain of Sputnik Planitia that looked like nothing else. Few craters, so it's young. And towering over it, enormous mounds with lumpy, hummocky sides.
The biggest, Wright Mons, stands 4 to 5 kilometers high and about 150 kilometers across. Its neighbor, Piccard Mons, rises about 7 kilometers. The volume of Wright Mons alone is similar to Mauna Loa, Hawaii's giant volcano.
In 2022, a team studying the New Horizons data proposed that this whole region was built by cryovolcanism: icy volcanism, where instead of molten rock, a slush rich in water ice wells up from below. They think it erupted from many sites, perhaps over more than one episode, piling up domes that merged together. Nothing like them has been seen anywhere else in the Solar System.
That's surprising, because Pluto's surface sits around −220 °C and the dwarf planet was thought to have little heat left inside. If the team is right, Pluto kept more warmth inside than anyone expected, enough to move ice late in its history. Nobody has seen one erupt, so this is an interpretation of the landscape, not an observation.
A small, frozen world far from the Sun may still have been building mountains.
6. 🕳️ PKS 2131-021 keeps time like a metronome
Quasars are the blazing hearts of distant galaxies, powered by giant black holes. Their brightness usually flickers at random. So when Caltech astronomers, monitoring more than a thousand of them, noticed in 2020 that PKS 2131-021 was rising and falling in a smooth, perfect wave, they went digging.
PKS 2131-021 is about 9 billion light-years away, and its jet, a beam of matter moving at nearly the speed of light, points almost straight at us. The team searched old radio records and found the wave had been there between 1975 and 1983, disappeared for about 20 years, and then came back with the same rhythm and timing. "We knew something very special was going on," said Sandra O'Neill, then an undergraduate at Caltech.
The best explanation is two supermassive black holes orbiting each other every two years or so. As the black hole with the jet circles, its beam swings slightly toward and away from us, so we see it brighten and dim like a lighthouse. The pair would be about 2,000 times Earth's distance from the Sun apart, and could merge in roughly 10,000 years.
It's still a candidate, not a confirmed pair. But something 9 billion light-years away is keeping very good time.
7. ⭐ VVV-WIT-08 almost vanished from the sky
A survey watching a billion stars in the crowded middle of the Milky Way sometimes finds things that fit no category. The team calls them "WIT" objects, short for "what is this?"
VVV-WIT-08 is a giant star, about 100 times wider than the Sun and more than 25,000 light-years away. For years it shone steadily. Then it faded to just 3% of its normal brightness, bottoming out in April 2012, and took a few hundred days to recover. In 17 years of observations, it happened only once.
It dimmed equally in visible and infrared light, so whatever blocked it was completely opaque, not a thin veil of dust. And it was huge: at least a quarter of the Earth–Sun distance thick.
A random dark object drifting past by chance seems unlikely; there would have to be an implausible number of them. Instead, the team thinks the star has an unseen companion wrapped in an opaque disk, which passes in front of it once every few decades.
"It's amazing that we just observed a dark, large and elongated object pass between us and the distant star," said Sergey Koposov. Nobody yet knows what the companion is. For a few hundred days, something we can't see swallowed a giant.
8. 🪐 WASP-189b's air is made of rock, in the same recipe as its star
Some giant planets orbit so close to their stars that they're hotter than a furnace. WASP-189b, about 320 light-years away in Libra, is one of these ultra-hot Jupiters. It's hot enough that rock-forming elements like magnesium, silicon and iron float in its atmosphere as vapor.
That makes it a rare chance to measure what rocks are made of on a world we can't visit. Using a sensitive instrument on the Gemini South telescope in Chile, Jorge Antonio Sanchez, a graduate student at Arizona State University, and colleagues measured magnesium and silicon in a planet's atmosphere at the same time, for the first time.
The ratio of magnesium to silicon in WASP-189b matches its star.
That sounds modest, but astronomers have been relying on it for years. Since we can't sample a distant rocky planet, we usually measure its star and assume the planet was built from the same mix, because both formed from the same cloud. That mix shapes a rocky world's interior, its magnetic field and plate tectonics. Until now, the assumption rested on our own Solar System.
A planet hot enough to boil rock has confirmed that worlds inherit the recipe of their stars.
9. 🛰️ Spacecraft flying past Earth picked up speed nobody could explain
Space missions often swing past Earth to borrow a little of its momentum on the way somewhere else. Navigators can predict these flybys extremely precisely. So it was strange when, in 2008, JPL's John Anderson and colleagues reported that several spacecraft came out slightly faster or slower than they should have.
They looked at six flybys by Galileo, NEAR, Cassini, Rosetta and MESSENGER, and found anomalies in five. NEAR gained about 13 millimeters per second, just a millionth of its speed, but far bigger than the 0.1 millimeters per second the radio tracking could measure. The one clean flyby, MESSENGER's, approached and left Earth at almost mirror-image latitudes north and south of the equator. "I am feeling both humble and perplexed," Anderson said.
For nearly two decades, ideas came and went. In September 2026, a team reran Rosetta's 2005 flyby using ESA's new deep-space navigation software and the original tracking data. Rosetta's later flybys of Earth had shown no boost at all. They reproduced the boost and ruled out errors in Earth's position, its gravity map and relativity. Their suggestion: sunlight reflected off Earth warmed sensitive parts of the spacecraft and made them release gas, giving it a tiny push.
That covers only one flyby. The best explanation for a cosmic puzzle may be a spacecraft gently breathing out in Earth's light.
10. 💥 SN 2026gzf was caught from its very first flash
When a massive star's core collapses, a shock wave races outward and bursts through the star's surface in a flash of X-rays called a shock breakout. It's the very first light of a supernova, and it lasts seconds to hours, so it's almost always missed. In two decades, astronomers had confidently caught only one clear X-ray breakout.
In March 2026, the Einstein Probe X-ray telescope spotted a faint flash of X-rays from a galaxy about 500 million light-years away. Within an hour, telescopes on the ground were watching a supernova brighten in the same spot: SN 2026gzf.
It turned out to be the kind of supernova that often comes with a gamma-ray burst, the most powerful kind of explosion we know, driven by jets moving at nearly the speed of light. But this time there was no burst and no jet, and the breakout was the faintest ever linked to this type. One idea is that the jet was "choked," smothered inside the star or by material around it.
The star that died was a Wolf-Rayet star, born with about 20 times the Sun's mass. Before it exploded, it had thrown off all its hydrogen and helium in fits and starts, leaving shells of gas around a core of carbon and oxygen.
Stars that look alike can die in more ways than we thought.
11. 🪐 Saturn's rings grow ghostly spokes
Saturn's rings look perfectly smooth and orderly. Then, every so often, faint smudges appear across them, stretched out like the spokes of a wheel.
Voyager 2 first photographed these spokes in 1981, and Cassini saw them during its 13 years at Saturn. They rotate along with the rings, fade after two or three trips around the planet, and can be longer and wider than Earth.
Hubble checks on Saturn every year, and it has found that spokes come in seasons. Saturn is tilted like Earth, and each season lasts about seven years. The number and darkness of the spokes change with those seasons, and astronomers expect the most activity around Saturn's equinox, when the rings are tipped less steeply away from the Sun. In 2021 the spokes appeared only on one side of the rings. By 2023, they showed up on both.
"The leading theory is that spokes are tied to Saturn's powerful magnetic field, with some sort of solar interaction," said Amy Simon of NASA Goddard. The idea is that electric forces lift fine dust or ice just above the rings, where it catches the light differently.
But after more than four decades of watching, no theory predicts them perfectly. Saturn's rings have weather, and we still can't forecast it.
12. ⭐ BLAPs are stars that pulse in minutes
Many stars pulse, swelling and shrinking in a steady rhythm. Big, cool stars take days or months. So astronomers were surprised in 2017 when the OGLE survey in Poland found more than a dozen hot stars pulsing every 20 to 40 minutes.
They're called blue large-amplitude pulsators, or BLAPs. Their surfaces are about 30,000 degrees, around five times hotter than the Sun's. Each cycle they brighten and fade by roughly 20 to 45%, in a sharp sawtooth pattern like the famous pulsing stars called Cepheids. Their temperatures and colors change through each cycle, proving the stars themselves are swelling and shrinking.
That's the strange part. No known kind of star, hot or cool, makes such big pulses so fast. The best guess is that they're small, aging stars with puffed-up outer layers rich in helium, but nobody knows how a star would end up that way.
In October 2025, the OGLE team finished searching more than 400 million stars and found 88 more, bringing the total to almost 200, with periods from about 5 to 76 minutes. Three of them are changing their rhythm surprisingly fast.
Somewhere in our galaxy, a star finishes a full breath in less time than it takes to drink a cup of tea.
13. 🌌 Andromeda's heart has three hearts
In 1993, Hubble looked at the center of the Andromeda Galaxy and saw something odd: two bright clusters of stars instead of one. Two clusters that close should have merged within a few hundred thousand years.
Scott Tremaine of Princeton suggested an answer. The "double nucleus" is really one stretched-out ring of old, red stars orbiting a central black hole. It looked like two clusters because we were mostly seeing the stars at its opposite ends.
Then there was a third light, a faint blue glow first spotted in 1995. In 2005, Hubble finally resolved it: more than 400 hot young stars packed into a disk only a light-year across, born in a burst about 200 million years ago. They whip around at about 1,000 kilometers per second, fast enough to circle Earth in 40 seconds. Their speed weighed the black hole at about 140 million Suns, and ruled out every alternative.
But stars shouldn't be able to form so close to a black hole. Its pull should tear gas clouds apart first. "Seeing these stars is like watching a magician pulling a rabbit out of a hat," said Tod Lauer. As Ralf Bender put it, "star formation looks almost impossible. But the stars are there."
At the center of our nearest big neighbor, there's a nursery where no nursery should be.
14. 🌌 MoM-z14 is a galaxy that shines too brightly, too early
When we look far into space, we look back in time. In January 2026, Webb confirmed a galaxy called MoM-z14, seen just 280 million years after the Big Bang, a new distance record at the time. Its light has been traveling for about 13.5 billion years, stretched into the infrared by the expanding universe along the way.
Before Webb launched, theorists expected galaxies that early to be few and faint. Instead, Webb keeps finding bright ones, about 100 times more than predicted. "It looks nothing like what we predicted, which is both challenging and exciting," said Rohan Naidu of MIT.
MoM-z14 adds another puzzle: a lot of nitrogen. Elements like nitrogen are made inside stars, and there shouldn't have been time for many generations of stars to build up so much. One idea is that the crowded early universe made supermassive stars, far bigger than any we see today, which could make nitrogen quickly. Curiously, some of the oldest stars in our own galaxy carry the same unusual nitrogen.
MoM-z14 also seems to be clearing the fog of hydrogen gas around itself, one of the first steps in letting light travel freely through the universe.
The universe's childhood was busier and brighter than anyone imagined.
15. 🌌 Future astronomers may never learn about the Big Bang
Everything we know about the beginning of the universe rests on three clues. Distant galaxies are rushing away from us. A faint glow, the cosmic microwave background, fills the sky. And the amounts of the lightest elements match what the Big Bang should have made.
In 2007, physicists Lawrence Krauss and Robert Scherrer asked what would happen to those clues in the far future. Their answer is quietly haunting.
The universe's expansion is speeding up. Our Local Group of galaxies is held together by gravity, but everything beyond will be carried away. On a timescale of about 100 billion years, it will all slip out of reach, its light stretched until it can no longer be seen. Astronomers then would see only one island of stars, made from our own neighborhood, surrounded by darkness, with nothing to show that space is expanding.
The background glow will fade too. By then it will be about a trillion times weaker, and later its waves will grow too long to pass through the thin gas between the stars. And after many more generations of stars, the original mix of light elements will be lost.
Those future astronomers, the authors argue, would conclude they live in an unchanging island universe, just as astronomers believed in 1900. The evidence for the beginning is written across the sky only for a while, and we happen to be here while it is.
🌙 One last thought before you sleep
So much of tonight was about memory.
Tree rings remembered a storm on the Sun. Old star clusters remembered a galaxy the Milky Way swallowed almost 12 billion years ago. A planet's air remembered the recipe of its star, and a quasar's light kept the same rhythm across decades of radio records.
The universe keeps its records everywhere, in carbon and in starlight, in orbits and in chemistry. Astronomy is the patient work of learning to read them.
And the last story tells us that some records won't last forever. The glow of the Big Bang, the retreat of the galaxies: these are messages with an expiry date, and we happen to be living while they can still be read.
We arrived in time to read the universe's oldest letters. Not everyone will.
That's all for tonight. Thanks for wondering along with me. Good night, and clear skies. 🌌
— Kasi