Telescopes around the world saw a bright flash appear around a distant and supermassive black hole. And then, very quickly, it disappeared.
the dungeon – the heavy nucleus of a galaxy called 1ES 1927 + 654 – was visible from land Due to its corona, the ring of overheated particles rotating around its event horizon, or point of no return for falling matter. There was nothing special in this state of affairs; Throughout space, astronomers can detect supermassive black holes thanks to their luminous crowns. And this corona was nestled within an apparently ordinary active galactic nucleus (AGN), or a larger region of dust, gas, and star clusters.
But in March 2018, the crown of this black hole briefly shone extra bright. The All-Sky Automatic Survey for Super-Novae (ASSASN), a group of 24 Ohio State University telescopes around the world designed to hunt supernovae, reported a 40-fold increase in brightness.
“This was an AGN we knew about, but it wasn’t very special,” said Erin Kara, a MIT physicist and lead author of an article about the event. statement. “Then they noticed that this current AGN suddenly became bright, which caught our attention, and we started targeting many other telescopes at many other wavelengths to look at it.”
After the AGN turned on, it suddenly dimmed. The black hole at its center, which can be best seen using X-ray telescopes – Seemed to get 10,000 times less shine in less than a year.
“We expect luminosity changes of this size to vary on time scales of thousands to millions of years,” Kara said. This region, meanwhile, “but on this object, we saw it change by 10,000 over a year, and it even changed by a factor of 100 in eight hours, which is totally unknown and truly mind-blowing.”
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However, the attenuation did not last. After the initial 8-hour darkening period, the crown continued to dim for much of the next year. Then, in a span of a few months, the black hole lit up again. It now looks almost exactly like it did before the crown flashed and disappeared.
So what happened?
Scientists aren’t sure, but Kara and her colleagues have a theory.
We detect black holes primarily due to their accretion disks, the rings of matter spinning around them, of which the corona is only the innermost, fastest-moving part.
Black holes feed and grow by sucking on their accretion disks. It is difficult for something to fall directly across the event horizon without first separating and spending time circling around it. (This is true for any heavy object in space; it is much more difficult to fall in the sun(for example, what it is to orbit.) Much of the matter in an accretion disk eventually falls into the black hole, but only after a long period of surrounding the drain.
For something to come out of an accretion disk and fall into a black hole, physicists think that something has to push that object. Usually the culprit is turbulence. But if something heavy, probably a star, collided with the corona of 1ES 1927 + 654, the star could have broken and disturbed the accretion disk enough to hit matter in orbit in the black set in one go. Researchers call this type of event a “tidal disruption.”
In that case, the first bright flash would likely have been the opening of the star by hitting the crown. The massive gravity of the black hole would have overwhelmed the gravity that held the star together, shattering it.
The precipitous 8-hour drop in luminosity would have been the initial disruption of the accretion disk tide. A large amount of gas, dust, and plasma that had been orbiting in circles before the star arrived would have fallen beyond the event horizon at once, struck by the collision with the star. And then the biggest attenuation over a period of months would have been the remaining, pushed matter falling from a now unstable orbit.
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A rebellious star could also have disrupted the magnetic field lines around the black hole. A black hole’s magnetic field can help hold a high-energy corona – the magnetic field lines that hold the rotating high-energy material in place. A collision with a star could disrupt that field long enough for the corona to crumble.
If that’s what happened here, it’s a big problem.
Scientists don’t understand much about the crowns of black holes, including the locations of the magnetic field lines that keep them intact. But they do know that a black hole the size of 1ES 1927 + 654 would have to get closer to about 45 million miles (75 million km) from the singularity itself to be attracted. That’s not much more than Mercury’s distance from the sun.
If a star interrupts the magnetic fields of the black hole after falling apart at that distance, that suggests that the lines of the corona and the magnetic field are also so far from the black hole. From Earth, the crowns of black holes are too close to their central singularities to directly measure the distances involved. So that’s a big problem.
“With the caveat that this event occurred due to a disruption of the stellar tide, this would be one of the strictest restrictions we have on where the corona should exist,” Kara said. “We want to keep an eye on her … She’s still in this unusual high-flow state, and maybe she’s going to do something crazy again, so we don’t want to miss that.”
Originally published in Live Science.
