Scientists at Stanford University in California, in partnership with Canadian and Dutch researchers, were able to observe Einstein’s theory of general relativity in action: by analyzing the corona of a supermassive black hole, they found light coming from behind the structure. The discovery was detailed in an article published on July 28 in the scientific journal Nature.

The new observations confirm a key prediction of general relativity: the detection of photons curved around the black hole at the back of the disk. In the observed galaxy, I Zwicky 1, located 800 million light-years away, a series of X-ray flashes were seen emanating from the corona of a black hole. But the telescopes registered something unexpected: additional flashes of X-rays that were smaller and had different “colors” to the glare and that came from behind the structure.

Black Hole
Illustration shows a black hole

The images agree with the theory being developed by Dan Wilkins, astrophysicist and lead author of the study. Wilkins has constructed theoretical predictions of how black hole echoes appear to us. When he saw the smallest flashes in telescope observations, he discovered the connection of the images to his theory.

“The analysis of the X-ray bursts reveals short photon flashes consistent with the resurgence of emission behind the black hole. The energy changes of these photons identify their origins in different parts of the disk”, explained the researcher in the article with the results of the observation.

Black holes and the theory of general relativity

According to the astrophysicist, the reason we can see the smaller flares coming out from behind the black hole is because it’s warping space, bending light and twisting the magnetic fields around itself. So Einstein was right again.

Characterizing and understanding black hole coronas will still require further observation, which should become easier with the construction of the European Space Agency (ESA) X-ray observatory, the Advanced Telescope for High Energy Astrophysics (Athena).

Wilkins is helping to develop part of Athena. The equipment has the largest mirror in an X-ray telescope, which will allow obtaining higher resolution images in less time. Evolution must better understand the coronas of black holes and how these regions behave.

Article Nature: doi.org/10.1038/s41586-021-03667-0