Sagittarius A* believed to be a black hole at the center of our Milky Way galaxy, became subject of recent study. "'The Awakening' --When Will the Supermassive Engine at the Heart of Our Galaxy Reignite?" - title of recent The Daily Galaxy article, where astronomers wonder why galactic core seems relatively quiet? A team of astronomers used X-Ray satellites from Japan, the United States and Europeans Union to partially determine history of the black hole. The picture (left) is an image of the black hole, captured by the Chandra X-Ray Observatory. Perhaps, most interesting, the method used by team to discover something about the black hole's history:
"It turns out that, approximately 300 years ago, Sagittarius A* let loose, expelling a massive energy flare. Data taken from 1994 to 2005 revealed that clouds of gas near the central black hole, known as Sagittarius B2, brightened and faded quickly in X-ray light. The X-rays were emanating from just outside the black hole, created by the buildup of matter piling up outside the black hole, which subsequently heats up and expels X-rays.
These pulses of X-ray take 300 years to traverse the distance between Sagittarius A* and Sagittarius B2, so that when we witness something happening in the cloud, it is responding to something that happened 300 years ago.
Amazingly for us, in a rare occurrence of perfect cosmic timing, a region in Sagittarius B2, only 10 light-years across varied dramatically in brightness. "By observing how this cloud lit up and faded over 10 years, we could trace back the black hole’s activity 300 years ago," said Katsuji Koyama of Kyoto University. 'The black hole was a million times brighter three centuries ago. It must have unleashed an incredibly powerful flare.'"