X-Rays Can Echo and Bend Around the Back of Supermassive Black Holes
Astronomers have spotted these echoes before, but this is the first time they have been able to see echoes from the area of the accretion disc directly behind a black hole. “If we think about it naively, it should be hidden from our view, but because of the strong gravity of the black hole, these echoes are being bent so we can see them,” says Dan Wilkins. This confirms a prediction from Albert Einstein’s general theory of relativity about how light should behave under the influence of extreme gravity. The ability to see echoes from behind a black hole could also give us a new perspective on how accretion discs — which are some of the brightest objects in the sky — work.