Wow. A black hole may have fallen into a star, eating it up and causing three big gamma ray bursts! Never seen before.
The first gamma ray burst was detected by the Fermi Gamma-ray Space Telescope on July 2, 2025. The second came 47 minutes later. The third came 188 minutes after that. These bursts were also seen by X-ray detectors.
At first people thought these bursts were coming from within our galaxy. But a day later, the Very Large Telescope found they were from a distant galaxy. This was soon confirmed by the Hubble Space Telescope. So they had to be very powerful.
Repeated powerful bursts like this over a long period of time are unprecedented. Now a careful analysis has come out, which argues that they came from a black hole falling into a 'helium star'. This is a blue supergiant star that's already blown off its outer hydrogen layers, leaving a core of helium. It would be more massive and vastly larger in size than a 3-solar-mass black hole, which is just 18 kilometers across. So the black hole could fall in and then rapidly suck in gas, causing huge gamma ray bursts.
I'm not quite sure why they think it was a helium star - the paper is not easy to follow for nonexperts like me - but I think it's because these stars are massive yet smaller in size than a giant or supergiant. They also considered the scenario of a black hole falling into a white dwarf, but rejected it.
These graphs show gamma rays as a function of time, detected by various detectors.
(1/2)