Observing the X-rays emitted into the Universe by a supermassive black hole, scientists discovered strange flashes that turned out to be a reflection received from the backside of the hole. This is the first direct observation of light coming from behind a black hole-a phenomenon predicted by Einstein’s general theory of relativity but not confirmed until now. The results of the study are published in the journal Nature.
Stanford University astrophysicist Dan Wilkins studied a supermassive black hole at the center of a galaxy 800 million light-years away when he noticed something unexpected. Along with bright X-ray flashes, the telescopes recorded additional flashes that appeared later than the main ones, were less bright, and of different “colors.” According to calculations, these reflections, or light echoes, corresponded to X-rays reflected from the backside of the black hole.
“Any light that enters a black hole does not come out of it, so we should not see what is behind the black hole,” Dan Wilkins, a researcher at the Institute of Particle Astrophysics and Cosmology and the National Accelerator Laboratory SLAC of Stanford University, is quoted in a press release by the university. — The reason we can see this is because a black hole bends space, deflects light, and twists magnetic fields around it.”
Initially, the study was aimed at studying the corona, an element that some black holes possess. The material falling into a supermassive black hole feeds the brightest continuous light sources in the universe and, in doing so, forms a corona of X-ray light around the black hole.
The existing theory states that the formation of this element begins with the sliding of gas into a black hole, where it overheats to millions of degrees. At this temperature, the electrons are separated from the atoms, creating magnetized plasma. Then, captured by the powerful rotation of the black hole, the magnetic field bends over the black hole and rotates around itself so much that it eventually completely collapses. The situation is similar to what happens around the Sun. Therefore, by analogy with the solar corona, scientists called this phenomenon the corona of a black hole.
“This magnetic field bound and close to the black hole, heats everything around and produces these high—energy electrons, which then create X-rays,” explains Wilkins. — For several years, I have been making theoretical predictions about what these echoes will look like for us, so as soon as I saw them through a telescope, I realized what they are related to.”
“Fifty years ago, when astrophysicists started thinking about how a magnetic field could behave near a black hole, they had no idea that one day we would have methods that would allow us to observe this directly and see Einstein’s general theory of relativity in action,” says another author of the study, Professor Roger Blandford from the Stanford School of Humanities and Natural Sciences, as well as professor of physics and particle physics at SLAC.
The authors will continue to describe and study the crowns of black holes. They place special hopes on the European Space Agency’s Athena space telescope, which is scheduled to launch in 2031.