Discovered a new kind of black holes that can wake up and fall asleep

Astronomers from all over the world constantly find blackholes in different galaxies, and often such an object can be supermassive - millions of times heavier than the sun. Black holes behave differently: they can gradually absorb the surrounding gas or a whole star at once. And some, as it turned out, can suddenly "wake up", thus accelerating the accretion rate, and then fall asleep again.

Scientists from the Swiss Higher Technical SchoolZurich discovered such a black hole - after its awakening, it increased the brightness of its galaxy by almost 50% in just two months. This fact became known after studying the outbreak, first seen in early 2017. Astronomers decided that between 2004 and 2017 there was a sharp increase in the UV radiation of the AT 2017bgt flash. Moreover, this is not a discontinuity of the star, which is sometimes observed when a black hole is absorbed by stars: this is evidenced by the slow evolution of the light curve and the features of the detected AT 2017bgt spectrum.

According to the researchers, they managed to openA new way of “feeding” black holes. According to the hypothesis put forward, a flash occurred as a result of the acceleration of the accretion of matter onto a supermassive black hole with a mass of about 1.8 × 107 solar. Other known ways to accelerate the growth of a black hole, as a rule, take much longer. In the past, scientists were able to record only two events that proceeded in a similar way.

The galaxy in which the new phenomenon took place,is 900 million light years from Earth. The mass of a black hole is 1.8 × 10 in the seventh power of the sun. By the way, scientists are not fully aware of how such objects reach such impressive sizes.

Now astronomers are celebrating a 75-fold increase.radiation in the ultraviolet range, but the black hole itself "hibernated" again after 2017. True, the question of whether it was completely inactive before the outbreak remains open.

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