Light behind a black hole measured for the first time

For the first time, astrophysicists have succeeded in seeing reflected light from behind a black hole. This experiment confirms Einstein's theory.

Updated version of the previous article.

Surely the only thing you've heard so far is that nothing, not even light, can escape from a black hole. But this is not entirely true about black holes.

Anything that crosses the event horizon (the outer edge of a black hole) is lost forever, but the hot disc of matter swirling around the black hole can emit powerful X-rays as seen from Earth  .

However, not all this light is easily passed out. As X-rays emanating from a supermassive black hole at the center of a galaxy 800 million light-years away, Stanford University astrophysicist Dan Walkins observed some strange flashes of X-rays.

They were shorter X-rays, came later and had different wavelengths for the normal, more luminous emission, as were thought to be echoes.

As described in a study led by Walkins in Nature, these flashes are reflected from behind black holes – a strange place for light to come from.

"Any light that goes into that black hole doesn't come out, so we shouldn't be able to see anything behind the black hole," Walkins explains.

The reason we can see it is because the black hole is rotating space, bending light and rotating the magnetic field around it.

As a black hole spins, it is the incredibly strong magnetic field that surrounds it and becomes so entangled that the field lines eventually break – as happens on the surface of our Sun.

'This magnetic field tied up and then snapped close to the black hole heats everything around it and produces these high-energy electrons that go on to produce X-rays' Walkins says.

These X-rays try to escape the black hole's enormous gravitational pull, but some are eventually pulled back, then reflected off the back of the disc and ejected into space.

Some of these 'echoes' from behind the black hole are bent around it by extreme gravity, creating the light observed by Walkins and his team.

This is the first time astronomers have directly observed light from behind a black hole, based on research published last year that found 'imprints' of such reflected light.

Observing such signals will allow astronomers to develop a better understanding of the black holes themselves. 

(This article originally published by cosmosmagzine)

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