Galaxies form as massive clouds of gas condense under gravity to form stars. Early galaxies have been predicted to form stars much more quickly and burn through their stellar fuel, leaving behind dead galaxies, unable to form new stars. JWST discovered several massive galaxies in the early universe that matched this, but astronomers wonder 'Why?'. A new study using JWST and ALMA looks at Cristal-02 — a 1.1 billion year-old galaxy — that is being blown apart by stellar winds created by rapid supernova explosions and could shed new light as to why some early galaxies could form and die in short periods.
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Astro Brief is a podcast collaboration between KSMU, the Missouri Space Grant, and MSU's Department of Physics, Astronomy and Materials Science. Hosted by Dr. Mike Reed, Astro Brief focuses on astronomical events, the field of astronomy, and astronomy-related guests. It airs Thursdays at 9:45 am on KSMU.
Transcript
In this episode, we're going to talk about galaxies that live fast and die young. Considering that our galaxy is roughly 12 billion years old, some context is needed.
Interestingly, almost everything in our universe begins as gas and ends as gas. So gas is the main topic for this episode.
Roughly 12 billion years ago, a giant, giant lump of gas roughly a trillion times the mass of our sun and possibly even a million light years across began to gravitationally contract — not everywhere at once like a balloon losing air, but more likely in a variety of regions. Those regions formed the first stars within our galaxy, usually in large groups of up to a million or so stars. By the time our galaxy had aged a couple billion years, the gas had flattened into a spinning disk, which was also now forming stars in spiral arms.
Our early disk formed stars at roughly a rate of about 10 solar masses per year. After a few billion years, that slowed down to a few stars per year with some slightly faster or slower periods, depending on when our galaxy absorbed gas from eating small galaxies.
Our galaxy is now forming stars at a rate of about six per year and that rate has been fairly steady for the past billion years or so. That rate would slowly decline over the next several billion years as gas is used up, where our galaxy left to itself.
However, our galaxy eventually will collide with Andromeda — the other large galaxy in our local group — in somewhere between 5 and 10 billion years. When that happens, stars likely will not hit each other, but pressure on the gas will create a burst of star formation and that will quickly — and by quickly I mean over hundreds of millions of years — use up the gas and then star formation will end. So while our galaxy has been using its gas to form stars in a slow and steady pace, that collision with Andromeda will create a burst of star formation and then a dead galaxy.
While galaxies have sufficient gas to be forming stars, astronomers consider them alive. And when there is insufficient gas — so no new stars — we consider them dead. Very human of us.
That history of our own galaxy brings us to the topic for this episode.
The James Webb Space Telescope has been looking far away, so back in time to when our universe was very young, looking for the very first galaxies. And it was expected that those young galaxies would be hives of active star formation. Indeed, some of those have been found. However, JWST also found several massive yet dead galaxies before the universe was even a few billion years old.
As reported in the Astrophysical Journal in a 2025 study led by Dr. Andrea Weibull at the University of Geneva, JWST detected a massive yet dead galaxy when our universe was only 700 million years old. Something was happening, much unlike our own galaxy's slow and steady approach to star formation that was causing these galaxies to live fast and die young.
One possible explanation was that perhaps dark energy was stronger in the early universe causing galaxies to grow faster and use up their gas quicker. Since astronomers use the word dark in place of unknown or mysterious, it would be easy to modify it to do what's observed. However, when dark energy was first discovered, it was also called vacuum energy, indicating it was caused by a lack of matter, which our young universe didn't have.
A more recent paper by Dr. Rebecca Davies of Swindburne University and collaborators, published in monthly notices of the Royal Astronomical Society, has likely found the answer. They found a galaxy in the early universe with an extremely strong wind blowing away this star-forming gas.
The galaxy — called Cristal-02 — was observed by JWST and the Alma Observatory in Chile. They are observing this galaxy at a time when our universe was only 1.1 billion years old. While Cristal-02 is now a single galaxy, it is a merger of several smaller galaxies, which is expected in the early universe when it was smaller and galaxies were closer together. During those mergers, star formation goes into overdrive, forming huge quantities of massive stars which live briefly, then violently explode in supernovas. The large number of supernovas is driving a wind so strong that Cristal-02 is losing gas twice as fast as its forming stars.
Dr. Davies predicts that in less than another 50 million years — or when the universe was only 1.15 billion years old — Cristal-02 will be a massive dead galaxy.
JWST observations indicate that about half of early massive galaxies are either multiple mergers or interacting with nearby galaxies. So this discovery by Dr. Davies and collaborators could provide the explanation for young, yet dead galaxies in the early universe.
Perhaps JWST has discovered and subsequently solved another new phenomenon of our universe.