What happens when a massive star dies — but doesn't explode?
We tend to picture stellar death as spectacular. A blinding supernova that outshines an entire galaxy. Shockwaves ripping through space. A cosmic fireworks show. But what if some stars simply… vanish? Quietly. No flash. No bang. Just darkness where light used to be.
Welcome to FreeAstroScience.com, where we explain complex scientific ideas in plain, clear language — because we believe the sleep of reason breeds monsters, and your mind deserves to stay awake and curious. Today, we're telling you the story of M31‑2014‑DS1: a star in our neighboring Andromeda Galaxy that apparently collapsed straight into a black hole, and nobody noticed for years. Grab a coffee, settle in, and read this all the way through. By the end, you'll never look at a starlit sky the same way again.
A Star Vanished Without a Bang — And It's Rewriting What We Know About Black Hole Birth
What Actually Happened to M31‑2014‑DS1?
Somewhere in the Andromeda Galaxy — about 2.5 million light-years from your screen — a supergiant star with roughly 13 times the mass of our Sun reached the end of its road. Rather than erupting in a brilliant supernova, it did something far stranger. It brightened briefly in infrared light, starting around 2014, then over the next several years it simply… faded away.
By 2019, the star had dimmed by a factor of more than 100 in optical light. By 2022, it was more than 10,000 times fainter than it once was. And when the ground-based MMT Observatory pointed at that location in 2023? Nothing. The star was gone.
This discovery was published on February 12, 2026, in the journal Science, led by Kishalay De, an astronomy professor at Columbia University, along with a team of 13 co-authors from institutions like Harvard, MIT, Caltech, and Princeton.
"This has probably been the most surprising discovery of my life. The evidence of the disappearance of the star was lying in public archival data and nobody noticed for years until we picked it out." — Kishalay De, Columbia University
The star's name is M31‑2014‑DS1. And what we believe happened to it is something theoretical physicists predicted decades ago but had barely witnessed: a failed supernova that formed a stellar-mass black hole.
How Do Massive Stars Normally Die?
Let's set the stage. Stars with initial masses greater than about 10 solar masses (M☉) live fast and die young — at least by cosmic standards. Near the end of their lives, they expand, become variable, and undergo dramatic luminosity shifts we can observe from Earth.
When a massive star exhausts its nuclear fuel, its core can no longer support itself against gravity. The core collapses. That collapse releases an enormous flood of neutrinos — ghostly particles that barely interact with matter. Those neutrinos drive a powerful shockwave outward into the star's outer layers, called the stellar envelope.
The Classic Supernova Scenario
If that shock is strong enough, it rips the envelope apart and hurls it into space at thousands of kilometers per second. The result? A core-collapse supernova — an explosion so luminous it can temporarily outshine an entire galaxy, exceeding 107 solar luminosities. What's left behind is either a neutron star or, for more massive progenitors, a black hole.
These violent deaths are relatively easy to spot. Modern optical surveys detect them routinely. But here's the catch — and this is where it gets interesting.
Not every massive star dies with a bang.
What Is a Failed Supernova?
In some massive stars, the neutrino-driven shock simply isn't powerful enough. It stalls. It fails to eject the envelope. And when that happens, most of the stellar material falls back onto the collapsing core.
Think about it this way: the star tries to explode, but gravity wins. The outer layers — all that gas, all that mass — come crashing inward, feeding the growing compact object until it becomes a stellar-mass black hole. The star doesn't go out in a blaze of glory. It goes out like a candle being snuffed.
A failed supernova occurs when a massive star's core collapses, but the resulting shockwave can't eject the stellar envelope. Instead, the envelope falls back onto the core, forming a black hole. The star disappears with little or no visible explosion.
This isn't a wild guess. Theoretical models have predicted failed supernovae for years. But actually catching one in the act requires monitoring individual stars across entire galaxies, over years or even decades. That's an enormous challenge. As De put it: "Unlike finding supernovae which is easy because the supernova outshines its entire galaxy for a few weeks, finding individual stars that disappear without producing an explosion is remarkably difficult."
The Evidence: A Star That Faded Into Darkness
So how did they find M31‑2014‑DS1? The team applied an image subtraction pipeline to data from NASA's NEOWISE (Near-Earth Object Wide-Field Infrared Survey Explorer) mission. They analyzed mid-infrared (MIR) observations of the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33) taken every six months from 2009 to 2022.
They were searching for luminous infrared transients — the kind of faint, dusty glow that would accompany a stellar eruption or a failed supernova. Among millions of sources, one stood out.
The Timeline of Disappearance
Here's what makes this so compelling: the fading wasn't just in one wavelength. The researchers tracked both optical and infrared light simultaneously. When some stars dim in visible light due to dust formation, their total energy output stays the same — the light is simply reprocessed and re-emitted at longer infrared wavelengths. Their bolometric luminosity holds steady.
That didn't happen here. As M31‑2014‑DS1 faded in optical light, there was no compensating increase in infrared brightness. The star's total luminosity genuinely dropped. Nuclear fusion had stopped. The core had collapsed.
And there was no supernova. If one had occurred, existing surveys would have easily spotted it. None did.
The Physics Behind the Collapse
Let's get into the mechanics of how this works — because the physics here is genuinely beautiful, even if the outcome is a bit terrifying.
Free-Fall Time
If the star were collapsing purely under its own gravity, the outer envelope would fall inward on roughly its free-fall timescale:
Here, G is the gravitational constant and ρ is the star's average density. A pure free-fall collapse would swallow everything in about seven months. But the observations show the bolometric luminosity continued fading over more than 1,000 days — far longer than 210 days. Why?
Energy Injection and Delayed Fallback
During core collapse, the initial loss of gravitational binding energy (roughly 0.2 to 0.5 M☉ worth of mass-energy) gets released as neutrinos. Some of that energy, along with feedback from inefficient accretion, gets injected into the outer envelope. The team's models explored shock energies between 1045 and 1049 erg — weak compared to a typical supernova's ~1051 erg, but enough to slow the collapse.
This injected energy does two things:
First, it ejects a small fraction of the outer envelope — less than about 0.1 M☉ of material — at the star's escape velocity of roughly 60 km s−1. That ejected material eventually cools and forms dust, producing the brief infrared brightening seen in 2014.
Second, it delays the fallback of the remaining material, stretching the process from ~210 days to over 1,000 days.
The Eddington Limit and the Luminosity Plateau
As material rains down onto the growing black hole, the accretion rate initially far exceeds the Eddington accretion rate — the maximum rate at which matter can fall in while still allowing photons to escape. During this super-Eddington phase, the emerging luminosity gets capped near the Eddington luminosity:
This explains the roughly 1,000-day plateau the team observed: the source luminosity held steady at about 30–50% of LEdd, even as mass was pouring in faster. Once the infall rate dropped below the Eddington limit, the luminosity began decaying in step with the falling accretion rate — exactly what the observations show.
Dust Condensation Timescale
The ejected material travels outward until it reaches the dust condensation radius (rc), where temperatures drop enough for solid dust grains to form. The timescale for this is:
That's consistent with the timing of the peak mid-infrared brightness. The pieces fit together with striking precision.
Where Did Most of the Mass Go?
The models with shock energies of 1047 to 1048 erg best match the observed fading. In those scenarios, about 98% of the stellar mass collapses or falls back, leaving behind a black hole of approximately 5 M☉. Since the maximum mass of a neutron star tops out around 2–3 M☉, the remnant has to be a black hole.
Portrait of the Progenitor Star
Before its demise, M31‑2014‑DS1 had been observed by both the Hubble Space Telescope and the Spitzer Space Telescope between 2005 and 2012. It was even cataloged as an irregular variable star, designated V7984 M31B, and classified as a candidate red supergiant based on its near-infrared colors.
But when the team fitted its spectral energy distribution (SED) with a model of a blackbody photosphere surrounded by a circumstellar dust shell, a different picture emerged. The star was actually a yellow supergiant — warmer than a classic red supergiant, with an effective temperature of about 4,500 K. Its apparent redness came from being shrouded in dust, with a mass-loss rate of roughly 10−4 M☉ per year.
| Property | Value |
|---|---|
| Designation | M31‑2014‑DS1 (V7984 M31B) |
| Host Galaxy | Andromeda (M31), ~2.5 million light-years |
| Celestial Coordinates (J2000) | RA 00h45m13s.47, Dec +41°32′33″.14 |
| Spectral Classification | Yellow supergiant (hydrogen-depleted) |
| Initial Mass | ~13 M☉ |
| Terminal Mass (at death) | ~5 M☉ |
| Hydrogen Envelope Mass | ~0.28 M☉ |
| Progenitor Luminosity | ~105 L☉ |
| Effective Temperature | ~4,500 K |
| Dust Shell Temperature | ~870 K at ~110 AU radius |
| Mass-Loss Rate | ~10−4 M☉ year−1 |
| MIR Brightening Onset | 2014 |
| Optical Fading Factor (2016–2019) | ≳100× |
| Total Luminosity Fading | ≳10,000× (optical), ≳10× (bolometric) |
| Inferred Shock Energy | 1047–1048 erg |
| Ejected Mass | ≲0.1 M☉ |
| Fraction of Mass Collapsed | ~98% |
| Resulting Black Hole Mass | ~5 M☉ |
| Free-Fall Timescale | ~210 days |
| Observed Fading Plateau | ~1,000 days |
What's fascinating is that the star's initial mass of ~13 M☉ falls right in the range where we'd normally expect a successful supernova. As De noted: "Stars with this mass have long been assumed to always explode as supernovae. The fact that it didn't suggests that stars with the same mass may or may not successfully explode, possibly due to how gravity, gas pressure, and powerful shock waves interact in chaotic ways with each other inside the dying star."
A Second Witness: NGC 6946‑BH1
M31‑2014‑DS1 isn't entirely alone in this story. There's a predecessor — a disappearing supergiant called NGC 6946‑BH1, first identified in the spiral galaxy NGC 6946, roughly 25 million light-years away. That object was spotted around 2010. It showed a luminous optical outburst (about 106 L☉), followed by an expanding dusty envelope, and then it too faded to a fraction of its original brightness within a few thousand days.
The problem with NGC 6946‑BH1 was distance. At ten times farther away than M31‑2014‑DS1, the data was fuzzier, the constraints weaker. Some researchers even wondered whether it might be a stellar merger rather than a failed supernova.
| Property | M31‑2014‑DS1 | NGC 6946‑BH1 |
|---|---|---|
| Host Galaxy | Andromeda (M31) | NGC 6946 |
| Distance | ~2.5 million light-years | ~25 million light-years |
| Progenitor Type | Yellow supergiant (H-depleted) | Yellow supergiant (initially classified as RSG) |
| Initial Mass | ~13 M☉ | ~17.5 M☉ |
| Terminal Mass | ~5 M☉ | ~7.5 M☉ |
| Hydrogen Envelope | ~0.28 M☉ | ~0.6 M☉ |
| Optical Outburst | Brief / likely missed due to cadence | Observed (~106 L☉, ~150 days) |
| Fading Timescale | ~1,000 days | ~3,000 days |
| Remnant Luminosity | ≳10,000× fainter than progenitor | ~15% of progenitor luminosity |
What De's team showed is that both events can be explained by the same model: massive, hydrogen-depleted stars whose cores collapsed without a successful supernova. NGC 6946‑BH1's slightly higher mass and more massive hydrogen envelope produced a brighter, longer-lasting outburst and a slower fading — exactly what the physics predicts. The two events reinforce each other.
"We've known that black holes must come from stars. With these two new events, we're getting to watch it happen, and are learning a huge amount about how that process works along the way." — Morgan MacLeod, Harvard University
Why This Changes Everything
Let's step back and think about what this means.
For decades, astronomers assumed a relatively clean relationship between a star's initial mass and its fate. Below about 8 M☉, you get a white dwarf. Above that, you get a supernova and either a neutron star or a black hole. Simple. Tidy.
M31‑2014‑DS1 shatters that tidiness. At ~13 M☉, this star sat comfortably in the "should explode" range. But it didn't. The relationship between a star's birth mass and whether it forms a black hole through a failed supernova appears to be complex and possibly chaotic for stars above about 12 M☉. Two stars with the same initial mass might meet completely different ends, depending on the messy, turbulent internal physics during their final moments.
How Common Are Failed Supernovae?
That's the million-dollar question. Using previous estimates for the fraction of massive stellar deaths that produce failed supernovae, the team calculated that the probability of finding at least one event in their search was just 1 to 20%. They found one. This was the largest study ever conducted of variable infrared sources across the stellar populations of nearby galaxies — and it yielded a single detection.
As De put it with a note of disbelief: "It comes as a shock to know that a massive star basically disappeared (and died) without an explosion and nobody noticed it for more than five years. It really impacts our understanding of the inventory of massive stellar deaths in the universe. It says that these things may be quietly happening out there and easily going unnoticed."
The Vera C. Rubin Observatory, expected to begin its decade-long Legacy Survey of Space and Time, has the potential to find many more of these silent collapses. With its ability to repeatedly survey vast stretches of sky at high sensitivity, it could turn a sample of two into a statistically meaningful catalog — and finally tell us just how often stars die in silence.
Why No X-rays?
If a black hole is actively accreting material, we'd typically expect X-ray emission. Archival X-ray observations of M31‑2014‑DS1 show no detection, and the same is true for NGC 6946‑BH1. The most likely explanation? The surrounding gas and dust absorb the X-rays before they can reach us. The newly formed black hole sits hidden behind a thick cocoon of its own making.
Conclusion
We've journeyed from a quiet patch of sky in the Andromeda Galaxy to the violent, invisible heart of a dying star. M31‑2014‑DS1 began life as a massive supergiant with about 13 solar masses. It shed most of its hydrogen envelope through fierce stellar winds. When its core finally gave out, the neutrino-driven shock wasn't strong enough to produce an explosion. Roughly 98% of the star's remaining mass collapsed or fell back, forming a ~5 M☉ black hole. No supernova. No fireworks. Just a slow infrared glow from a thin shell of ejected dust, then darkness.
Together with NGC 6946‑BH1 — the only other known candidate — this discovery gives us the first real observational evidence that failed supernovae happen, that stellar-mass black holes can form in near-total silence, and that the boundary between stars that explode and stars that simply vanish is far blurrier than we once thought.
There's something both humbling and deeply poetic about this. Not all cosmic deaths are loud. Some of the most massive objects in the universe — black holes — are born in whispers. And it took patient astronomers, poring over years of archival data, to hear them.
We at FreeAstroScience.com believe that understanding these cosmic processes enriches our view of the universe — and of ourselves. We exist to make complex science accessible, to keep your mind active and questioning, because the sleep of reason breeds monsters. Stay curious. Come back often. The universe has far more surprises in store.
Sources
- De, K., MacLeod, M., Jencson, J. E., et al. (2026). "Disappearance of a massive star in the Andromeda Galaxy due to formation of a black hole." Science, 391(6786). DOI: 10.1126/science.adt4853
- Gough, E. (2026, February 19). "No Supernova Needed. This Star Collapsed Directly Into A Black Hole." Universe Today. universetoday.com
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