Astronomers have witnessed a rare cosmic event: a massive star that didn’t explode in a spectacular supernova, but instead quietly collapsed into a black hole.
Astronomers have directly observed a dying massive star that did not explode in a supernova. Instead, it collapsed inward, forming a black hole. The event provides the most complete set of observations ever collected of a star making this transition, allowing scientists to piece together a detailed physical explanation of how it unfolded.
By combining new telescope data with more than ten years of archived observations, researchers were able to test and sharpen existing theories about how very massive stars end their lives. Rather than blowing apart in a dramatic explosion, the star’s core gave way under gravity and became a black hole. As that happened, its unstable outer layers were gradually pushed outward.
The findings, published February 12 in Science, are generating excitement because they offer a rare look at how black holes are born. The results could help explain why some massive stars explode at the end of their lives while others collapse quietly.
“This is just the beginning of the story,” says Kishalay De, an associate research scientist at the Simons Foundation’s Flatiron Institute and lead author on the new study. Light from dusty debris surrounding the newborn black hole, he says, “is going to be visible for decades at the sensitivity level of telescopes like the James Webb Space Telescope, because it’s going to continue to fade very slowly. And this may end up being a benchmark for understanding how stellar black holes form in the universe.”
An animation of a star that collapsed, forming a black hole. The black hole is at the center, unseen. Surrounding it is a dust shell moving away from the black hole and gas being pulled toward it. Credit: Keith Miller, Caltech/IPAC – SELab
The Disappearance of M31-2014-DS1 in Andromeda
The star, known as M31-2014-DS1, lay about 2.5 million light-years from Earth in the neighboring Andromeda Galaxy. De and his colleagues examined data collected between 2005 and 2023 from NASA’s NEOWISE mission along with other ground and space telescopes. They found that the star began to brighten in infrared light in 2014. Then in 2016, its brightness dropped sharply, fading far below its original level in less than a year.
Follow-up observations in 2022 and 2023 revealed that the star had nearly disappeared in visible and near-infrared wavelengths, dimming to just one ten-thousandth of its former brightness in those bands. What remains is detectable only in mid-infrared light, where it now shines at roughly one-tenth of its earlier intensity.
De says, “This star used to be one of the most luminous stars in the Andromeda Galaxy, and now it was nowhere to be seen. Imagine if the star Betelgeuse suddenly disappeared. Everybody would lose their minds! The same kind of thing [was] happening with this star in the Andromeda Galaxy.”
When the team compared the dramatic fading with theoretical predictions, they concluded that the star’s extreme drop in total brightness strongly indicates that its core collapsed into a black hole.
Why Some Massive Stars Fail to Explode
Stars produce energy by fusing hydrogen into helium in their cores. That fusion creates outward pressure that balances the inward pull of gravity. In stars at least 10 times more massive than our sun, this balance eventually breaks down as fuel runs low. Gravity then takes over, and the core collapses to form a dense neutron star.
In many cases, a burst of neutrinos released during the collapse triggers a powerful shock wave. That shock can tear apart the core and outer layers, producing a supernova. However, if the neutrino driven shock is too weak to expel the surrounding material, much of the star can fall back inward. Longstanding theory has suggested that this fallback can transform the neutron star into a black hole.
“We’ve known for almost 50 years now that black holes exist,” says De, “yet we are barely scratching the surface of understanding which stars turn into black holes and how they do it.”
Convection Shapes the Star’s Final Moments
The detailed observations of M31-2014-DS1 also prompted researchers to revisit another object, NGC 6946-BH1, first identified about a decade ago. Reexamining both cases led to a key insight into what happens to a star’s outer layers after a failed supernova. The missing factor was convection.
Convection arises from large temperature differences inside a star. The inner regions are extremely hot, while the outer layers are much cooler. This contrast causes gas to circulate, moving from hotter areas toward cooler ones.
When the core collapses, the outer gas is still in motion because of this churning process. Models developed by astronomers at the Flatiron Institute show that this motion prevents most of the outer layers from plunging straight into the black hole. Instead, some inner material circles the black hole, while the outermost layers are pushed away.
As that expelled material travels outward, it cools. At lower temperatures, atoms and molecules combine to form dust. This dust blocks light from the hotter gas near the black hole, absorbs energy, and then reemits it in infrared wavelengths. The result is a faint red glow that can persist for decades after the star itself has vanished.
Co-author and Flatiron Research Fellow Andrea Antoni developed the theoretical groundwork for these convection models. With the new observational evidence from M31-2014-DS1, she says, “the accretion rate — the rate of material falling in — is much slower than if the star imploded directly in. This convective material has angular momentum, so it circularizes around the black hole. Instead of taking months or a year to fall in, it’s taking decades. And because of all this, it becomes a brighter source than it would be otherwise, and we observe a long delay in the dimming of the original star.”
Much like water swirling around a drain rather than dropping straight down, gas continues to orbit the newly formed black hole as gravity gradually pulls it inward. Because convection slows the inward flow, the entire star does not collapse at once. Even after the core quickly gives way, some of the ejected material slowly falls back over many decades.
Researchers estimate that only about one percent of the star’s original outer envelope ultimately feeds the black hole, producing the faint light that can still be observed today.
A Growing Class of Failed Supernovae
As they analyzed M31-2014-DS1, the team also reexamined NGC 6946-BH1. The new study presents strong evidence explaining why that star followed a similar path. What once appeared to be an unusual case now seems to be part of a broader group of massive stars that collapse quietly into black holes.
M31-2014-DS1 initially stood out as an “oddball,” De says, but it now appears to be one example in a class of objects that includes NGC 6946-BH1.
“It’s only with these individual jewels of discovery that we start putting together a picture like this,” De says.
Reference: “Disappearance of a massive star in the Andromeda Galaxy due to formation of a black hole” by Kishalay De, Morgan MacLeod, Jacob E. Jencson, Elizabeth Lovegrove, Andrea Antoni, Erin Kara, Mansi M. Kasliwal, Ryan M. Lau, Abraham Loeb, Megan Masterson, Aaron M. Meisner, Christos Panagiotou, Eliot Quataert and Robert Simcoe, 12 February 2026, Science.
DOI: 10.1126/science.adt4853
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