For the first time, astronomers have directly detected light behind a supermassive black hole. The discovery proves that Albert Einstein’s theory of general relativity was right – again.
Using the European Space Agency’s XMM-Newton space telescopes and NASA’s NuSTAR, researchers observed the black hole as it projected X-rays into the universe. The black hole is about 10 million times as massive as our sun and is located at the center of a nearby spiral galaxy called I Zwicky, 1,800 million light years from Earth.
After observing a series of bright X-ray flares, something new happened: more lightning bolts that were smaller, later, and of different “colors” than their predecessors. According to a study published this week in the journal Nature, the “echoes” of light appeared to be consistent with X-rays reflected from behind the black hole – a very strange place for light.
The gravitational pull of black holes is so powerful that light cannot escape them. However, the light can “echo”, curl around the back of the celestial phenomenon and allow astronomers to see it.
“No light entering this black hole is going out, so we shouldn’t be able to see anything behind the black hole,” lead author Dan Wilkins said in a statement. “The reason we can see this is because this black hole distorts space, bends light, and twists the magnetic fields around it. ”
While Einstein predicted the ability of a black hole’s gravity to bend light around it in 1916, this has never been confirmed – until now.
“Fifty years ago, when astrophysicists began to speculate on the behavior of the magnetic field near a black hole, they had no idea that one day we could have the techniques to observe it directly and see the Einstein’s general theory of relativity in action, ”said co-author Roger Blandford.
The researchers weren’t even looking to confirm Einstein’s theory. They were originally trying to unravel the mysteries of a strange feature of black holes known as the corona, the source of the brilliant x-ray light.
“I’ve been building theoretical predictions on how these echoes appear to us for the past few years,” Wilkins said. “I had seen them before in the theory I had developed, so once I saw them in the telescope observations, I was able to understand the connection. “
The prevailing theory is that the corona forms after gas continuously falls into the black hole, forming a spinning disc around it, “like water flowing down a drain”. The gas disk is then heated to millions of degrees, generating a twisted magnetic field that eventually breaks, releasing its energy and producing the corona.
“This magnetic field that sets and then moves closer to the black hole heats everything around it and produces these high-energy electrons which then produce the x-rays,” Wilkins said.
From there, astronomers hope to use the different “colors” seen as X-ray echoes travel around the black hole to create a 3D map of the black hole’s environment. They also hope to learn how the crown produces such bright flares.
characteristic image – Dan Wilkins