Black Hole Corona Observed Vanishing and Reappearing For the First Time

A paper on the observation by MIT astronomers provides insight into the formation of coronas.
Chris Young

For the first time, astronomers at MIT and elsewhere have observed a supermassive black hole's corona, the ultralight, billion-degree ring of high-energy particles that surrounds the event horizon, mysteriously disappear and then reappear.

Researchers, who published their findings in Astrophysical Journal Letters, state the observation provides new insight into the formation of black hole coronas.


A dramatic and sudden disappearance

Though the cause of the dramatic and sudden destruction of the black hole is unclear, the researchers say that it may have been caused by a star caught in the black hole's gravitational pull.

Whatever the cause, the scientists first observed the shift when they realized that the black hole, called 1ES 1927+654, had dropped dramatically in brightness, by a factor of 10,000, over the course of just under a year.

Through observations in several wave bands, and especially in the high-energy X-ray band, they saw that the black hole's corona had completely and suddenly disappeared in a short time.

“We expect that luminosity changes this big should vary on timescales of many thousands to millions of years,” Erin Kara, assistant professor of physics at MIT said in a press release. “But in 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 just totally unheard of and really mind-boggling.”

Impressively, over the following months, the astronomers observed as the black hole began to slowly pull material from its outer edges in order to reform its accretion disk and corona, and almost retained its original luminosity.

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The formation of black hole coronas

The findings have allowed the astronomers insight into the formation of black hole coronas. Though physicists are not sure exactly why coronas form, they believe it is linked to the magnetic field lines that run through a black hole's accretion disk.

Viewing the "tidal disruption radius" for the event at 1ES 1927+654 allowed them to calculate the radius at which the corona for a supermassive black hole of the same size might form.

“With the caveat that this event happened from a stellar tidal disruption, this would be some of the strictest constraints we have on where the corona must exist,” Kara says.

The astronomers aim to keep an eye on the corona, which has since reformed, lighting up in high-energy X-rays. “We want to keep an eye on it,” Kara explains. “It’s still in this unusual high-flux state, and maybe it’ll do something crazy again, so we don’t want to miss that.”

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