The galaxy’s central black hole could have looked surprisingly different a few hundred years ago
New research shows that the X-ray light coming from the galaxy’s central black hole Sagittarius A* has changed dramatically over a period of just a few hundred years
NASA, ESA, CSA, STSCI, A. Ginsberg (University of Florida), N. Budayev (University of Florida), T. Yu (University of Florida). Image Processing: A. Pagan (STScI)
Supergiant black holes are mysterious objects. Scientists aren’t entirely sure how these beating hearts form at the centers of most large galaxies. This includes Sagittarius A* (Sgr A*), the supermassive black hole at the center of our own galaxy.
now a New preprint study is shedding light on Sagittarius A* by studying what happens when material falls toward a black hole.
Typically, as dust, gas and other material accelerates toward a supermassive black hole, black holes emit “absolute torrents of light,” says Steve DeCarby, a postdoctoral researcher in the department of physics and astronomy at Michigan State University and co-author of the new paper. However, Sagittarius A* is quite faint. “It’s only emitting a small stream of radiation,” says DeCarby.
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Yet this was not always the case. Rather, the work of DeCarby and his colleagues shows that the disk of material swirling around Sagittarius A* once emitted much brighter X-rays – up to 10,000 times brighter than those emitted today. Research shows that, incredibly, the same may have happened as recently as a few hundred years ago.
conclusion Was presented at a meeting of the American Astronomical Society earlier this month and has been accepted for publication Astrophysical Journal Letters.
The work is “very important,” says Joseph Michael, a postdoc at the Center for Astrophysics at Harvard and the Smithsonian. He says, “This tells us about the ‘recent’ history of Sagittarius A*” – something that was missing from the research record.
“This work showed something completely different from the SGR A* we know and love – it was incredibly bright,” says Michael.
DeCarby and his colleagues used a powerful new X-ray telescope called XRISM (X-ray Imaging and Spectroscopy Mission) to look at the clouds of molecular gas around the black hole. DeCarby explains that these clouds are thought to reflect X-rays coming from around the black hole, acting as a “cosmic mirror” into its past.
“We can know not only how bright Sagittarius A* is today, but also how bright it appeared 100 years ago and 1,000 years ago,” he says.
To put its changes in brightness into perspective, the brightest observed X-ray flare came from Sagittarius A* in 2013But that was only about 1 percent of the brightness emitted by the black hole in that event, which probably happened as recently as a few hundred years ago, Michael says.
“Effectively, XRISM is telling us that something significant has happened to black holes over the last few centuries,” says Michael. However, it still remains a mystery.
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