A few hundred years ago: Trace of an eruption of the black hole Sgr A*
The supermassive black hole at the center of the Milky Way apparently flared up dramatically relatively recently. An echo of this was found.
Infrared image of a molecular cloud near Sagittarius A*
(Image: NASA, ESA, CSA, STScI, Adam Ginsburg (University of Florida), Nazar Budaiev (University of Florida), Taehwa Yoo (University of Florida); Image Processing: Alyssa Pagan (STScI))
Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is one of the most inconspicuous we know. However, a massive eruption apparently occurred relatively recently. This is the finding of an analysis with the XRISM space telescope, which has found traces of a “dramatic flare-up” a few hundred to a maximum of 1000 years ago. This is reported by Michigan State University in the USA, where one of the involved researchers works. He and his team have thus used the Japanese X-ray telescope to measure an echo of this eruption from a molecular cloud in the immediate vicinity of Sgr A*. Their goal is now to create a timeline of the black hole's activity based on other such echoes.
Hope for further findings
As the research group recalls, numerous supermassive black holes are much brighter than their name suggests. Because they accelerate and heat gas in their orbit extremely, they even emit a particularly large amount of high-energy radiation. In the center of the Milky Way, it looks different: Sagittarius A* is among the dimmest we know. If it weren't so close to us, we wouldn't be able to detect it. At the same time, however, it is orbited by clouds of different molecules, which could function like cosmic mirrors, explains the research group. So far, however, reflected signals could only be received as a much too weak glow. Only the space telescope launched in 2023, with the full name X-Ray Imaging and Spectroscopy Mission, was now powerful enough for more.
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Only XRISM, in measuring the X-ray radiation, has a resolution high enough to detect these echoes. The change is like going from a Polaroid to a high-resolution Technicolor photo, explains the team, also because the instrument can measure the energy of individual X-ray photons.
It does not provide more details about the eruption of the supermassive black hole responsible for the echo, but it must have been considerable. By measuring different molecular clouds, a chronicle of such eruptions could be created, says the team. The current research work is to be presented in an article in the journal The Astrophysical Journal Letters, which is not yet publicly accessible.
(mho)
