Scientists have noticed something amazing happening in Andromeda, our neighboring spiral galaxy located about 2.5 million light years away from Earth. The fantastic part is exactly what they are. was not WATCH: Instead of exploding as a bright supernova, a massive star that used to be there appears to have disappeared.
This case of “now you see it, now you don’t” is not some proverbial magic trick; It appears that a black hole is being born right before our far-seeing eyes. The observation may represent a failed supernova – a highly sought-after discovery due to a somewhat embarrassing fact: despite the ongoing renaissance in black hole studies that has revolutionized our understanding of these mysterious objects, even now, no one really knows how they form.
Scientists hope that capturing a black hole emanating from a dying star could change that.
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Astronomers know that stars of about eight solar masses or more eventually collapse under their own weight when they run out of thermonuclear fuel in their cores. The upper layers fall inward, compressing the core into a city-sized ball of neutrons – a neutron star – and rebound outward from the core in shockwaves that shake the star. When the shockwaves reach the surface the star explodes as a supernova, leaving behind a naked neutron star.
But for reasons that remain unclear, this obliterating shockwave within the most massive stars sometimes fades out, causing the supernova to fail. The star remains intact – until its unstoppable explosion due to gravity creates a black hole in its place.
Andromeda’s vanishing star wouldn’t be the first time astronomers have reported a glimpse of a black hole born without a supernova, but it would be the closest, best candidate seen so far.
“I got goosebumps when I saw it disappear into the darkness.” – Kishlay Dey, Astronomer
At least, that’s the conclusion of the study that was led by Columbia University astrophysicists Kishley Day and published today In Science. In 2022, Day and his colleagues began searching for failed supernovae among nearby galaxies using archival data from NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission, an infrared space telescope that mapped the sky from 2009 to 2024. In the fall of 2023 Day found what he was looking for, located in Andromeda (also known as Messier 31, or M31): a yellow supergiant star about a dozen times more massive than our Sun that had begun to shine in 2014 and then faded, disappearing from NEOWISE’s view entirely by 2022. The team named the star M31-2014-DS1.
“I got goosebumps when I saw it disappear into the darkness,” recalls Day.
Astronomers had estimated the probability of a failed supernova in any large spiral galaxy to be once per century, so discovering one in the galaxy’s next-door neighbor was almost too good to be true. Because Andromeda is a popular astronomical target, Day’s team could search records from several other world-class telescopes to confirm the star’s strange transitions in infrared, optical and ultraviolet light. Stranger still, instead of seeing a stream of high-energy radiation from a nascent black hole feasting on stellar remnants, Hubble Space Telescope data from 2022, as well as follow-up ground-based observations made in 2023, revealed a dim, reddish blob where the star once shone.
Day says the blob was probably the loosely bound outermost layers of a dying star that fell away as it collapsed. A small portion of that material probably fell back, burning up with X-rays and entering the black hole; The rest would have formed an extended, cool shell of light-absorbing dust, glowing faintly from otherwise hidden fireworks flashing deep within. “This is a prediction that has been going on for almost 50 years,” says Dee – and it is Supported by new comments With the James Webb Space Telescope (JWST) and the Chandra “When you look at the JWST data, it all fits perfectly,” Day says. (However, those comments arrived too late to be added to the researchers’ list Science paper and has yet to be peer-reviewed.)
After extensive computational modeling of the star’s death, Day and his co-authors concluded that M31-2014-DS1’s failed supernova produced a black hole of about five solar masses that was obscured by an ejected cloud of gas and dust with about a tenth the mass of our Sun.
Their model also neatly explained puzzling observations of the previous best candidate for a failed supernova, NGC 6946-BH1. This object, discovered more than a decade ago by Ohio State University astronomer Christopher Kochanek and colleagues, is difficult to study because it is about 10 times farther away than M31-2014-DS1 – and thus about 100 times fainter.
Kochanek—who was not part of Day’s study—agrees with the new results. Yet, he says, the team’s unified model faces an unavoidable problem in its reliance on dust—”one of the most notorious havens of scoundrels in astronomy.” That is, dust is so versatile that it can be used as an interpretive catchall; For almost any set of confusing astronomical observations, some carefully designed configuration of dust, for all its strangeness, can be resorted to. And this flexibility cuts both ways.
Already, another peer-reviewed study has challenged Day’s analysis—though neither he nor Kochanek find it credible. Led by astrophysicist Emma Beausore of Liverpool John Moores University in England and published mid january Monthly Notices of the Royal Astronomical Society, It uses Day’s JWST and Chandra data to reach a completely different conclusion: M31-2014-DS1 and NGC 6946-BH1 may be similarly rare cases of dust-covered stellar mergers – two stars colliding and joining – rather than black-hole-birthing failed supernovae.
“Everyone is excited to see a failed supernova – including me,” says Beasor. “But I would argue that we don’t yet have models that make very clear predictions about what they should look like. So before we confirm any, what I want to do is rule out every other possible scenario that could cause a star to ‘disappear’.”
Time will tell which interpretation proves correct, Kochanek says, because one very clear model-independent prediction remains: A stellar merger will brighten, while a black hole will darken. “And dust can’t obscure things forever,” he says. “In both of these scenarios, this dust is in an expanding shell, so the ‘veil’ will become thinner as the shell expands.”
However, this could take decades – potentially exhausting the planned lifetime of JWST, the best observatory for such follow-up studies, bar none. That’s why broadening the search to discover more candidates with next-generation facilities such as the ground-based Vera C. Rubin Observatory in Chile and NASA’s soon-to-launch Nancy Grace Roman Space Telescope could prove important, says Suvi Gizzari, an astronomer at the University of Maryland who was not part of these studies.
“Given those future capabilities, we can find more of these events to better determine whether they are all failed supernovae or stellar mergers or fusions,” she says. “Reading these papers, all I could think about is how exciting it is to enter this era where we will have many more opportunities to study this phenomenon.”
