Scientists think a supermassive black hole called Sagittarius A* lurks at the center of the Milky Way. Recent observations of this area show that clumps of gas orbit at about 30 percent of the speed of light on a circular path just outside the black hole's event horizon, according to a statement from the European Southern Observatory (ESO).
Using the GRAVITY instrument on ESO's Very Large Telescope, astronomers detected flares of infrared radiation coming from the accretion disc surrounding Sagittarius A*. Their findings not only confirm the presence of the supermassive black hole but also suggest that material is orbiting incredibly close to the black hole's event horizon. What's more, the recent observations offer the most detailed view yet of material orbiting so close to a black hole, according to the statement. [The Strangest Black Holes of the Universe]
"It's mind-boggling to actually witness material orbiting a massive black hole at 30 percent of the speed of light," Oliver Pfuhl, one of the study researchers and a scientist at the Max Planck Institute for Extraterrestrial Physics, said in the statement. "GRAVITY's tremendous sensitivity has allowed us to observe the accretion processes in real time in unprecedented detail."
Monster black holes lurk at the centers of most galaxies in the universe. Gravitational forces from these cosmic behemoths draw in surrounding gas and dust. Most matter in the accretion disc surrounding the Milky Way's black hole orbits at a safe distance. However, anything that gets too close risks being drawn past the event horizon, where it can never escape from the black hole's gravitational pul. The flares originate from material in the innermost stable orbit according to the statement — the closest matter can get before passing the point of no return.
Astronomers recorded the bright infrared emissions as they observed a star called S2 pass through the extreme gravitational field near Sagittarius A* in May 2018.
During the star's close flyby, the team saw the strong infrared emissions coming from highly energetic electrons located very close to the galaxy's black hole. Specifically, they found that the emissions originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*. Astronomers observed the emissions using GRAVITY, as well as the SINFONI instrument, which is also part of the VLT.
"We were closely monitoring S2, and of course we always keep an eye on Sagittarius A*," Pfuhl said in the statement. "During our observations, we were lucky enough to notice three bright flares from around the black hole — it was a lucky coincidence!"
Their findings were published Oct. 18 in the journal Astronomy & Astrophysics.