Have astronomers witnessed the birth of a black hole?

"A bright star in a nearby galaxy has essentially vanished. Astronomers believe that it died and collapsed in on itself, transforming into the eerie cosmic phenomenon known as a black hole. "It used to be one of the brightest stars in the Andromeda galaxy," says Kishalay De, an astronomer with Columbia University and the Flatiron Institute. "Today, it is nowhere to be seen, even with the most sensitive telescopes.""

"In the journal Science, he and his colleagues report that they noticed this disappearing star as they went looking through archival data collected over about 15 years by NASA's NEOWISE spacecraft. De says their plan was to make a map of how stars change in brightness in infrared light, so they set out to track the changes in millions of stars over time. One star, they noticed, was a real outlier."

"Around 2015, it suddenly brightened for about a year. After that, it abruptly started fading away, in both infrared light and the optical light that human eyes can see. Just a few years later, in optical light, it was completely gone. Scientists had known about this star for decades, and people used to be able to see it from their backyards, using small telescopes, notes De. But now, "we can't even detect this source today with the Hubble Space Telescope.""

Observations of a bright star in the Andromeda galaxy reveal a sudden 2015 brightening followed by an abrupt fade in both infrared and optical wavelengths until optical disappearance. Archival NEOWISE infrared data spanning about 15 years and follow-up imaging show the source is undetectable with Hubble and only marginally visible in faint infrared with JWST. The behavior matches a massive star exhausting nuclear fuel and collapsing into a black hole, with residual infrared glow produced by stellar material falling into the newly formed black hole. Continued monitoring predicts gradual fading over decades as accretion diminishes.

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