Data from the orbiting Chandra X-ray Observatory on emissions from gas clouds in the normally dim region very close to the supermassive black hole showed they've flared up with at least two luminous outbursts in the past few hundred years.
The most probable cause of the outbursts was light echoes, NASA reported Thursday.
If material from a star or planet fell into the black hole, the episodes would create X-rays that would have bounced off gas clouds about 30 to 100 hundred light years away from the black hole.
Just as echoes of sound reverberate long after the original noise was created, so too do light echoes in space replay the original event, astronomers said.
The X-ray echoes suggest that the area very close to the black hole, also known as Sagittarius A*, was at least a million times brighter within the past few hundred years.
Astronomers said they believed at least two separate outbursts were responsible for the light echoes observed by the Chandra observatory.