Light cannot escape from a black hole, but for the first time ever, researchers have observed light from behind a black hole — a scenario that was predicted by Einstein's theory of General Relativity but never confirmed, until now. In a paper published July 28 in Nature, a team including a Penn State scientist report recordings of X-ray emissions from the far side of a black hole.
Watching X-rays flung out into the universe by the supermassive black hole at the center of a galaxy 800 million light-years away, the researchers noticed an intriguing pattern. They observed a series of bright flares of X-rays — exciting, but not unprecedented — and then, the telescopes recorded something unexpected: additional flashes of X-rays that were smaller, later, and of different “colors” than the bright flares.
“I have been studying the X-ray properties of this remarkable active galaxy since the mid-1990s,” said W. Niel Brandt, Verne M. Willaman Professor of Astronomy & Astrophysics and professor of physics at Penn State and a member of the research team. “Back then, with much more limited X-ray data, my team established that it showed remarkable X-ray properties, including characteristic strong X-ray variability. This strong variability turned out to be important for deriving this unprecedented result.”
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Illustration 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. Researchers have reported the first recording of these X-ray echoes consistent with X-rays reflected from behind the black hole. (Photo Credit: Dan Wilkins)