While it is normal for the supermassive black hole to fluctuate slightly in brightness, the researchers found Sagittarius A*—which is four million times the mass of the sun—had gotten 75 times brighter than normal. “I was pretty surprised at first and then very excited,” Do told the news site.
…the researchers say the flash happened over a two-hour time span. They said the increase in brightness could suggest a change in activity at the supermassive black hole. Another cause could be a change to its accretion state—how the black hole is drawing matter inwards.