Astronomers are aware the supermassive black hole at the center of the Milky Way occasionally flares due to clouds of material suddenly being absorbed. These are not, however, the only emissions detected near the black hole. Researchers report the detection of flickering at millimeter wavelengths.
“It has been known that Sgr A* sometimes flares up in millimeter wavelength,” lead author Yuhei Iwata, a graduate student at Keio University, Japan, said in a statement. “This time, using ALMA, we obtained high-quality data of radio-wave intensity variation of Sgr A* for 10 days, 70 minutes per day. Then we found two trends: quasi-periodic variations with a typical time scale of 30 minutes and hour-long slow variations.”
These changes and the possibility of studying them are exciting to better understand black holes, but it's not good news for the Event Horizon Telescope. The collaboration was able to snap the first-ever picture of a black hole last year. In their campaign of observations, they also observed Sagittarius A* but they reported that the analysis of that data was a lot more complex than the M87 one that was published.
“In general, the faster the movement is, the more difficult it is to take a photo of the object,” stated co-author Professor Tomoharu Oka, also at Keio University. “Instead, the variation of the emission itself provides compelling insight for the gas motion. We may witness the very moment of gas absorption by the black hole with a long-term monitoring campaign with ALMA.”