Astrophysicists from Stanford University reported the fact of the first detection of light arriving from the region of space directly behind a black hole, which is a direct confirmation of one of the predictions of Albert Einstein’s general theory of relativity. During observations of the vicinity of a black hole, scientists recorded a number of bright flashes of X-rays, the appearance of which were expected events. But, unexpectedly for the scientists, the telescopes recorded additional X-ray flashes, which were of lower brightness and differed greatly in spectrum from the “foreground” flashes.
Scientists assumed that the phenomenon they observed was X-rays reflected in some way from the region of space immediately behind the black hole. However, the light that entered the black hole can no longer go back out, and we should not see anything behind the black hole. But, the strongest gravitation and magnetic fields around a black hole create distortions of the space-time continuum around it, which act like light guides through which the light, refracting, rounds the event horizon of a black hole.
The scenario described above is one of the predictions of Einstein’s general theory of relativity, which has never yet been confirmed experimentally or by astronomical observations. Moreover, registering light “from behind a black hole” was not the goal of these studies, which simply wanted to learn more about one of the mysterious features of some black holes, called the term “Corona”.
It is known that matter trapped in the gravitational trap of a supermassive black hole is the basis of the brightest sources of light in the universe – quasars. Under certain conditions, this light forms around the black hole its corona, consisting of plasma superheated to millions of degrees. Most of the light emitted by the corona is in the X-ray part of the spectrum, and the data contained in this light allow not only to establish the exact location of the black hole itself, but also to measure some of its main parameters.
At temperatures of millions of degrees, atoms lose all their electrons, forming a remagnetized plasma. Due to the characteristics of the environment and the effects of gravitational forces, the resulting magnetic field bends and forms a high rotating arc, which decays and then forms anew closer to the black hole’s event horizon. The resulting surplus energy of the magnetic field heats the surrounding matter, producing high-energy electrons, which are the source of X-rays.
Naturally, the processes leading to the formation of a black hole corona are in fact much more complex than described above. And scientists are trying to figure out all the subtleties of what is going on, using all the space-based and ground-based X-ray instruments available to them, which will soon include the new Athena observatory of the European Space Agency.
