X-rays can echo and bend around the back of supermassive black holes

Supermassive black holes have an immense gravitational pull ClaudioVentrella/Getty ImagesSupermassive black hole's intense gravitational pull makes them bend light around them. This allows us to see the echo of the side otherwise hidden. Now we can see echoes from X-ray bursts coming from behind a blackhole, confirming general relativity.There are three parts to the area around a blackhole: the eventhorizon, which isnt a solid, but is often referred to as the surface of the black hole, the accretion disk where material accumulates before falling in, and the corona. This is a cloud filled with superheated particles located just outside the eventhorizon. The corona may emit powerful X-ray flares in some supermassive black hole.Dan Wilkins, Stanford University in California, and his colleagues used the NuSTAR X-ray telescopes and XMM -Newton X–ray telescopes to see the radiation flashes coming from the supermassive dark hole in a galaxy called I Zwicky1. They observed that a flare in X-rays could sometimes be followed by a second flash, which was slightly darker because radiation bounced off of the accretion disk in a kind of echo.AdvertisementThese echoes have been seen by astronomers before but this is the first time that they can be detected from the area of an accretion disk directly behind a dark hole. Wilkins says that it would be difficult to see, as it is hidden by our eyes. However, the strong gravity of a black hole makes it possible for these echoes to be seen.This confirms Albert Einstein's general theory about relativity regarding how light should behave when subject to extreme gravity. We may also be able to see the echoes behind a blackhole, which could give us a new perspective about how accretion disks, some of the most bright objects in the sky, work.Wilkins says that the gas falling into supermassive dark holes is an important factor in the formation of galaxies today. To understand how galaxies formed and how they got there, we need to have a deep understanding of these extreme objects.Journal reference: Nature, DOI: 10.1038/s41586-021-03667-0Subscribe to the Launchpad newsletter and take a journey across the galaxy every Friday!