The black hole sits in the constellation of Sagittarius at the very heart of the Milky Way.
Scientists have made a remarkable discovery of an eerie echo coming from a black hole that lies more than 25,000 light years from Earth and is four million times more massive than our Sun, according to American space agency NASA. The discovery by researchers at the Astronomical Strasbourg Observatory in France was made after they combined data from the space telescope NASA's IXPE (Imaging X-ray Polarimetry Explorer) and the Chandra X-ray Observatory on the black hole named Sagittarius A*. A study detailing the new discovery has been published in the journal Nature.
The high and low notes of the echo were sent out when the black hole emerged from a long period of dormancy some 200 years ago.
According to the study, Sgr A* consumed large amounts of gas and dust after waking up, causing brilliant X-ray light bursts. These bursts produced echoes that can be translated into sound waves on Earth.
"One of the scenarios to explain why these giant molecular clouds are shining is that they are, in fact, echoing a long-gone flash of X-ray light, indicating that our supermassive black hole was not that quiescent some centuries ago," said Frederic Marin, and lead author of the new study.
IXPE, which measures polarization of X-ray light, pointed at these molecular clouds for two periods of study in February and March 2022. When the data was combined with images from Chandra Observatory, astronomers were able to isolate the reflected X-ray signal and discover its point of origin.
"The polarization angle acts like a compass, pointing us toward the mysterious, long-gone source of illumination. And what lies in that direction? None other than Sgr A*," Riccardo Ferrazzoli, astrophysicist at the Italian National Institute of Astrophysics in Rome, was quoted as saying by NASA on its website.
Follow-up data could improve estimations of when the flare occurred and how intense it may have been at its peak, and will help determine the three-dimensional distribution of the giant molecular clouds surrounding the quiescent black hole.
Last year astronomers revealed the first-ever image of the black hole - or rather, the glowing ring of gas that surrounds its blackness.
The pull of gravity from black holes is so intense that nothing can escape, including light.
But when matter is sucked beyond the black hole's final boundary, known as the event horizon, it emits a massive amount of heat and light before disappearing into the darkness.