The temporary disappearance of the corona of a black hole

(ORDO NEWS) — For the first time in the history of black hole observations, astronomers managed to record an unusual phenomenon: a bright corona surrounding the event horizon of a black hole mysteriously disappeared for some time. An article about this was published in the Astrophysical Journal Letters .

What caused this phenomenon, scientists cannot yet answer with one hundred percent certainty. Most likely, the cause of the incident was a star that fell under the influence of the gravity of a black hole. Scientists compare it to “a pebble caught in a gearbox”: the star ricocheted through the corona, as a result all particles orbiting the object fell into the hole. This led to a decrease in the brightness of the object tens of thousands of times in just a year.

Unusual things happening to the object 1ES 1927 + 654 – a supermassive black hole in the center of one of the galaxies – was noticed in March 2018. The brightness of this object has sharply increased by about 40 times. “It got our attention, and we started pointing [at the object] many telescopes [operating] at different wavelengths to look at it,” says physicist Erin Kara of MIT.

Through close attention to 1ES 1927 + 654, researchers have followed how the object loses radiation intensity in almost all frequency ranges, especially in the high-energy X-ray range. This indicated that the black hole’s corona had almost completely evaporated. “We expect such dramatic changes in brightness to occur on timescales ranging from many thousands to millions of years,” says Erin Kara. “But we saw that this object changes tens of thousands of times in a year, and even in a hundred hours it changed 100 times, which is absolutely amazing.”

However, the black hole’s crown did not disappear forever. In just a few months , a disk of emitting matter gathered around the object again – in its brightness almost equal to the corona that the hole had before the “incident”. “It seems that we first saw how the crown first disappeared, but then recovered itself, and we observed it in real time,” the scientists write. “This is very important for understanding how a black hole’s corona heats up and feeds.”

They do not know exactly what leads to the formation of the corona, but they believe that it has something to do with the configuration of the magnetic field lines passing through the black hole’s accretion disk. According to astronomers, if a star really was the cause of such a jump in brightness, then it was torn apart by the gravitational attraction of the black hole, and parts of the matter were scattered over the accretion disk. Among other things, this could lead to a temporary break and deformation of the magnetic field lines of the hole. “This means that for any normal corona, magnetic fields within a certain radius are responsible for creating the corona,” the scientists summarize.

Depending on the mass of the black hole, there is a certain radius within which the star will most likely be attracted by the black hole’s gravity and collapse. This means that the magnetic field lines that support the existence of the corona must be within this “radius of destruction”. According to calculations, if the star really caused the temporary absence of a corona around the supermassive black hole 1ES 1927 + 654, it would begin to collapse within a radius of about four light minutes, or 75 million kilometers from the center of the black hole.

Earlier we wrote that a white dwarf set off on a high-speed flight through the Galaxy due to a supernova explosion, and new estimates of the size of the supermassive black hole J2157 * made it one of the largest and “hungry” in the Universe.


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