Space News Deep Dive: Rewriting Star Death

Article February 14, 2026

Dear readers, I want you to imagine my reaction when I got a phone call from MIT’s Kavli Institute for Astrophysics and Space Research a couple of weeks ago asking if Spacing Out would like to be involved in helping break the news that researchers had been able to watch a star in our neighboring galaxy Andromeda directly collapse into a black hole without going supernova, the first time such a thing had ever been seen. And now imagine me trying to maintain a professional tone on that phone call. I’d like to say I managed it, but we all know I didn’t.

Because this is big. This is confirmation that we need to update our understanding of something as basic as star death, something we thought we had a decent handle on, That doesn’t happen every day. So I’m going to do a bit of a deeper dive into this story than I had room to do in the newsletter and explore what we know about this phenomenon—and what we don’t!

 

What We Saw

Andromeda is our nearest large galactic neighbor and is the site for this most recent discovery. Credit: Brody Wesner via Wikipedia Commons
Andromeda is our nearest large galactic neighbor and is the site for this most recent discovery. Credit: Brody Wesner via Wikipedia Commons

Let’s start with what it actually was researchers saw happen in Andromeda. First, in case you are unfamiliar with this neighbor, Andromeda (sometimes referred to by its Messier Catalog number, M31) is the closest large galaxy to us. It’s frequently referred to as the closest galaxy to us, but it’s not by a long shot. However, everything else near us is a tiny dwarf galaxy, while Andromeda is on par with the Milky Way in size. It’s about 2.5 million light years away, which is close when you’re talking about distances to other galaxies. 

In this galaxy lived a big ol’ star with the pithy designation M31-2014-DS1. At 13 solar masses, this star was well into the mass range where the end of stellar fusion results in a supernova (see my blog post on how stars die for more information on that). While this is not as big as stars get, it’s very big. A more familiar star that I’ve been seeing it compared to would be Betelgeuse, Orion’s shoulder star (also a past blog subject), to give you a more recognizable reference.

At 13 solar masses M31-2014-DS1 was not as big as stars can get, but very few stars manage to reach that size. Credit: University of Colorado
At 13 solar masses M31-2014-DS1 was not as big as stars can get, but very few stars manage to reach that size. Credit: University of Colorado

Over the last decade or so this star had begun to noticeably brighten even farther. And then around 2023 it was suddenly just…gone. Not 100% gone, but all that was left of this stellar behemoth was a small light in the mid-infrared glowing with 1/10,000th its former brightness. So imagine if Betelgeuse just winked out all of a sudden and left us with a tiny infrared smudge.

In our experience stars don’t do that. They might fade or they might explode but they don’t just vanish into nothing. But here is a star that undisputably did so. So what the heck happened?

 

Sudden Death

When stars detonate in a supernova the explosion itself is not only obvious, but the stuff it leaves behind is also very distinctive. The Crab Nebula is such a supernova remnant. Credit: NASA/ESA/J. Hester and A. Loll
When stars detonate in a supernova the explosion itself is not only obvious, but the stuff it leaves behind is also very distinctive. The Crab Nebula is such a supernova remnant. Credit: NASA/ESA/J. Hester and A. Loll

People who have been reading the Spacing Out newsletter for a while may (or may not) remember the May 30, 2024 edition in which I had a small freakout about the prospect of stars collapsing directly into black holes without first going supernova. In that newsletter I highlighted a study looking at a system consisting of a black hole and a massive companion star. That black hole was definitely once a star, but the system held no evidence of a supernova explosion (and being among the most violent processes in the universe, those things tend to leave evidence of themselves behind).

That suggested the possibility that this black hole had skipped the supernova stage and collapsed directly into a black hole. At the time this went against literally everything I had ever learned about how big stars go, hence the freakout. But it also wasn’t actual proof of the theory of direct collapse black holes. That was just a potential explanation, and a pretty out-there one. A star just suddenly dying with no fanfare whatsoever? Crazy talk! And after all, we’d never actually seen such a thing happen.

But now we’re pretty sure we have! Because a massive star collapsing directly into a black hole would appear to simply wink out, just like M31-2014-DS1 did. What’s more, the direct collapse model would not only explain M31-2014-DS1’s disappearance, it would also explain that infrared smudge left behind.

 

Anatomy of a Star Death

When stars go, however they go, their cores tend to do one thing while their outer layers do another. Essentially the cores go inward and the outer layers go, well, outward. With smaller stars the core collapses to a white dwarf and the outer layers drift out and form a planetary nebula. When a big star detonates in a supernova the core collapses into a neutron star or a black hole and the outer layers explode outward. That’s what we’ve always seen happen anyway.

What appears to have happened to M31-2014-DS1 is that its core did the collapse thing all stellar cores do when the star dies. It just skipped the explosive rigamarole that usually accompanies this event. That means the outer layers didn’t explode outward—they’re still surrounding the black hole.

This artist’s impression shows what we think M31-2014-DS1 looks like now: a hot, dense, bright core immediately around the black hole surrounded by the gases that used to be the star’s outer layers. Credit: Keith Miller, Caltech/IPAC-SELab
This artist’s impression shows what we think M31-2014-DS1 looks like now: a hot, dense, bright core immediately around the black hole surrounded by the gases that used to be the star’s outer layers. Credit: Keith Miller, Caltech/IPAC-SELab

If we could see the area immediately around the black hole, it would actually appear very bright, the same way the regions at the centers of galaxies can be very bright around their supermassive black holes. That’s from all the gas around the black hole swirling in towards it, giving off a lot of energy as it does. That energy is light, yes, but also heat.

That means what we’ve got in M31-2014-DS1 is a hot dense thing surrounded by drifting shreds that used to be the star’s outer layers. That hot thing in the middle is warming those shreds, and when gas gets warm in space it tends to glow softly in the infrared. Which means the direct collapse model fits what we’re seeing with M31-2014-DS1 pretty darned perfectly.

And that means stars can directly collapse into black holes without going supernova. And that means it’s time to reconsider our knowledge of how stars die. And that’s incredible!

 

Rewriting the Textbooks

The fact that this happened in our galactic backyard implies something. If this was a super rare kind of event, the odds of one happening so close to us (astronomically speaking anyway) would be low. And that’s on top of of the evidence we’ve seen of other systems that may have undergone direct collapse in the past to get to where we see them today.

That means that stars just peacing out with no fanfare is probably happening right under our noses fairly frequently and we’ve just never noticed before. Which is nuts, but also very exciting because it opens up a new area of stellar physics.

This graphic represents what we used to know about how stars die. Now it’s time for us to update our understanding. Credit: Encyclopaedia Brittanica Inc
This graphic represents what we used to know about how stars die. Now it’s time for us to update our understanding. Credit: Encyclopaedia Brittanica Inc

Because here’s the thing: we don’t know why this happened! Why did M31-2014-DS1 go this route instead of the traditional supernova route? Just how frequently is this happening? What does this mean for how heavy elements, things critical for life that are traditionally created and scattered to the cosmos through supernova explosions, form and get distributed? We don’t know! We’ve only seen it happen once! But now we might know what to look for if we want to see it happen again.

Remember that M31-2014-DS1 brightened significantly before it vanished. Maybe that’s a precursor to this process, a sign that whatever it is that causes a star to just collapse instead of detonate is beginning. If that holds up, we can use it as a marker to seek out other stars that could be about to vanish. And if we see it happen more, maybe we can figure out just what the heck is going on. After all, we can be very clever creatures sometimes.

 

What’s Next?

As the remants of M31-2014-DS1 continue to evolve, the bright, hot area in the core immediately surrounding the black hole should become more visible. Credit: Ketih Miller, Caltech/IPAC-SELAb
As the remants of M31-2014-DS1 continue to evolve, the bright, hot area in the core immediately surrounding the black hole should become more visible. Credit: Ketih Miller, Caltech/IPAC-SELAb

Obviously, we’re going to keep studying this dead star as its remnants evolve. Over time, as those outer layers either drift away or get assimilated into the material falling into the black hole, that infrared glow should fade. As that hot core area becomes more exposed, we should start to see this remnant brighten with the x-rays that tend to be emitted from the regions around black holes. The Webb and Chandra Telescopes should come in handy for those observations.

Equally obviously, we’re going to start hunting for signs of this process happening to other stars. That will hopefully help us identify what mechanism is triggered inside the star that makes it do this and also just how often this is happening. That, in turn, will help us further evolve our understanding of how the universe works.

And in the meantime I’ll have to start changing how I talk about stellar lifecycles to my Planetarium audiences. I can’t just tell them it’s all planetary nebulas and supernovas anymore. There’s much more to it than that. And honestly? That’s awesome!