Astronomers recently captured a supermassive black hole that engulfs a star. It flared up just like its younger cousins when those black holes were eating a snack. It just took longer and was a million times brighter.
Astronomers have been observing the feeding habits of tiny black holes with stellar mass for decades. These black holes often orbit other stars and occasionally feed on them. As material approaches the black hole, it compresses into a thin accretion disk. The heat from this attachment produced “soft” radiation, usually ultraviolet. But as soon as the material of the pane thins out, an incandescent corona takes over, which emits “hard” radiation in the form of X-rays.
The whole process is completed in a few days.
Supermassive black holes also feed on their surrounding material, but astronomers long thought it would be impossible to watch this process in real time, as it would take millions of years to flare up and then transition to a “soft” one “Hard” phase.
But then TDE AT2018fyk happened. This is the name of a special flare that was observed in September 2018 by the All-Sky Automated Survey for Supernovae (ASASSN). It was a tidal outbreak that happens when a huge black hole rips apart an entire star before it eats it alive.
A team of astronomers led by Dheeraj “DJ” Pasham, a researcher at MIT’s Kavli Institute for Astrophysics and Space Research, followed up with further observations of the event.
“Everything is abrupt when there is a tidal disturbance,” says Pasham. “You suddenly get a puff of gas and the black hole suddenly wakes up and it’s like, ‘Whoa, there’s so much food – just let me eat, eat, eat until it’s gone.’ So it experiences everything in a short time. This enables us to study all of these different stages of accretion that humans know about in black holes with stellar mass. “
Over the course of two years, astronomers saw the whole chaotic story unfold: an initial flash, the formation of an accretion disk with its “soft” UV emission, the transition to “hard” X-rays and a final disappearance.
“We showed that when you’ve seen a black hole, in a sense, you’ve seen them all,” says Pasham. “If you throw a gas ball at them, they all seem to be doing more or less the same thing. They are the same beast in terms of accretion. “
“People know that this cycle takes place in black holes of stellar mass, which are only about 10 solar masses. Now we’re seeing this in something 5 million times bigger, ”says Pasham.
Aside from being really cool, these observations are only the second time astronomers have seen a corona form around a black hole.
“A corona is a very mysterious being, and in the case of supermassive black holes, humans have examined established corona but do not know when or how they formed,” says Pasham. “We showed that you can use tidal disturbance events to capture corona formation. I look forward to using these events in the future to find out what exactly Corona is. “