XMM-Newton Special Exhibit
Reflections of Past Outbursts
The central regions of our galaxy, the Milky Way, seen in X-rays by ESA's XMM-Newton X-ray observatory. (Credit: ESA/XMM-Newton/G. Ponti et al. 2015)
Today, the supermassive black hole at the center of the Galaxy is very quiet, but it wasn't always so. While surveying the Galaxy's center, astronomers noticed something remarkable – over a period of several years, different regions of molecular clouds seemed to turn on and off gradually, as if a bright light beam were sweeping slowly in front of it. By examining these reflections and by tracing them over time, astronomers concluded that the Galaxy's black hole had an outburst about 400 years ago, lasting for about 300 years, and finally turning off about 100 years ago. When it was "on", its intensity was about 1 million times higher than the present intensity, making it look similar to the supermassive black holes at the centers of AGN.
This series of images shows the reflections of an outburst from the black hole at the center of the Milky Way galaxy that occurred about 400 years ago. The numbered regions in The Bridge, which showed this behavior most clearly, turn on in succession. (Image Credit: APC/SAp-CEA/ESA)
Published: September 2016
Text Reviewed: September 2018