An echo of the black hole of the Milky Way is recorded by NASA’s IXPE satellite

The IXPE satellite identified an X-ray trail coming from the ‘Sagittarius A’ black hole in our galaxy

An international team of scientists found an X-ray echo from Sagittarius A (Sgr A), the supermassive black hole at the center of our galaxy. The finding infers that Sgr A was inexplicably activated 200 years ago and recovered its destructive potential, only to return to its customary period of calm.

The scientific community has clarified that the black hole in the center of the Milky Way is in a period of latency. Since its discovery in the 1970s, Sgr A* has not devoured significant amounts of matter around it, and indirect signals related to its presence, such as radio waves and X-rays, remain stable.

Recent readings from NASA’s IXPE (Imaging X-ray Polarimetry Explorer) satellite detected a remnant of these waves whose origin dates back to the 19th century and whose power is at least a million times greater than that currently emitted by Sagittarius A*. Scientists deduce that something got close enough to the black hole to activate it, thus ‘awakening’ its original power. The remnants of that cosmic feast are still found in the Milky Way in the form of X-ray echoes.

At this point it is worth clarifying that black holes do not emit X-rays. In fact, they emit practically nothing. The radiation in the form of X-rays comes from hot matter approaching the black hole’s event horizon, never to return. Thanks to readings of this kind of electromagnetic radiation, scientists can estimate a black hole’s size, mass, and even its growth rate.

The X-ray echo from 200 years ago is extremely powerful. The French National Center for Scientific Research compares the sudden activation of the Sgr A* black hole with the light of a small firefly lost in a forest that suddenly begins to illuminate with the same power as a sun.

Despite the readings and photos of Sgr A* and other similar objects, the scientific community still cannot explain the physical mechanism required for a black hole to transition from an inactive to an active state.

Black holes do not emit sound, but NASA scientists have managed to give them a sound dimension. Through a process known as sonification, audio engineers and astrophysicists translate black hole photos (generated by X-ray readings and other sources) into a binaural 3D sound equivalent. If we only had the sense of hearing, this is how we would experience Sgr A.

The IXPE satellite was launched in 2021 to support the Chandra X-ray space observatory. It is considered the little brother, but it has the unique ability to identify the origin of X-rays by analyzing their polarization (the direction in which electromagnetic waves oscillate). The identification of the echo of Sgr A* from 200 years ago can be considered his first great achievement.