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Sunday, September 26, 2021

Light echoes from behind a black hole detected for the first time

The new observations confirm a key prediction of Einstein’s general theory of relativity.

By: Science Desk | Kochi |
July 30, 2021 2:25:28 pm
black holeIllustration of a bright flare of X-ray emission and its echoes produced as gas falls into a supermassive black hole and reflects off of the gas falling into the black hole. (DAN WILKINS via PSU)

Nothing can escape from a black hole, not even light. For this reason, a black hole is indeed truly black. But now researchers have seen light bending and X-ray echoes from behind a supermassive black hole. The paper was published on July 28 in Nature and is a piece of evidence for Einstein’s theory of general relativity.

The researchers used two space-based X-ray observatories – NASA’s NuSTAR and the European Agency’s XMM-Newton – and studied a supermassive black hole called I Zwicky 1 in the SpacSeyfert 1 galaxy which is about a 100 million light-years from Earth.

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” said Stanford University astrophysicist Dan Wilkins, the first author of the new paper in a release. He is a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford and SLAC National Accelerator Laboratory. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself.”

Above black holes, supercharged particles and other magnetic activity produces high-energy x-rays. “This magnetic field getting tied up and then snapping close to the black hole heats everything around it and produces these high-energy electrons that then go on to produce the X-rays,” said Wilkins.

black hole The flares echo off of the gas falling into the black hole, and as the flares were subsiding, short flashes of X-rays were seen corresponding to the reflection of the flares from the far side of the disk, bent around the black hole by its strong gravitational field. (ESA/S. POLETTI via PSU)

While investigating another mysterious feature of black holes called the corona, the team saw bright flares of X-rays. Further studies revealed that the flashes, caused by x-ray pulses reflecting off disk of gas, were coming from the far side of a black hole.

“Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein’s general theory of relativity in action,” said Roger Blandford, a co-author of the paper, who is the Luke Blossom Professor in the School of Humanities and Sciences and Stanford and SLAC professor of physics and particle physics in a release.

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