Shadows of black holes will help test the theory of gravity

Shadows of black holes will help test the theory of gravity

Synthetic shadow shots of Sagittarius A * for the Kerr Black Hole (top row) and non-rotating dilaton black hole (bottom row). The left model is created by general relativistic magnetohydrodynamic simulations, and the right model is realistic observation conditions.

Scientists from the Institute of Radio Astronomy. Max Planck conducted a new study, calculating the first images of non-Einstein black holes: now they are difficult to distinguish from the standard.

One of the predictions of Einstein's theory of relativity was the existence of black holes. Despite recent observations in LIGO, direct evidence using EM waves remains elusive. Scientists have to continue searching radio telescopes. Recently, it was possible to compare models and realistic images of the shadow of an accreting supermassive black hole Sagittarius A * in the center of the Milky Way. The experiment was conducted for the general theory of relativity and the theory of gravity. The goal was to test whether Einstein black holes could be distinguished from alternative ones in the theories of gravity.

Not all matter photons falling into a black hole are captured by the event horizon. Some of them reach distant observers, because of which you can see a black hole in the form of a “shadow”. The size and shape will depend on the properties of the black hole and the theory of gravity. The greatest deviation from the theory of relativity is expected closer to the horizon of events. Alternative theories of gravity put forward various predictions about the characteristics of the shadow. Therefore, direct observations of Sagittarius A * offer a promising opportunity to test various guesses.

Scientists decided to study the evolution of matter that fell into two completely different types of black holes, and calculated the released radiation to create images. Also used real physical conditions to achieve maximum realism. To get the effects of black holes, realistic simulations of accretion disks with almost identical initial settings were used.

Surprisingly, using realistic resolutions, scientists have found that even non-Einstein holes can disguise themselves as normal. The analysis showed that there are theories of gravity, where black holes are capable of being masked by the laws of Einstein. It is believed that the general theory of relativity is correct, but future observations should remove all doubts. Information from the orbital pulsar, which the researchers are now looking for, will help get rid of ambiguities. Now they are planning to improve their search and review methods in order to obtain convincing evidence of the existence of a black hole shadow.

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