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The Andromeda galaxy, the closest spiral galaxy to our own Milky Way, has a supermassive blackhole at the center of it much like other galaxies. Because of its proximity to us, Andromeda – or M31 – is an excellent place to study just how the supermassive black holes in the centers of galaxies consume material to grow, and interact gravitationally with the surrounding material.
Over the course of the last ten years, NASA’s Chandra X-Ray observatory has monitored closely the supermassive black hole at Andromeda’s heart. This long-term data set gives astronomers a very nuanced picture of just how these monstrous black holes change over time. Zhiyuan Li of the Harvard-Smithsonian Center for Astrophysics (CfA) presented results of this decade-long observation of the black hole at the 216th American Astronomical Society meeting in Miami, Florida this week.
From 1999 to 2006, M31 was relatively quiet and dim. In January of 2006, though, the black hole in the center of Andromeda suddenly brightened by over 100 times, and has remained 10 times as bright since. This suggests that the black hole swallowed something massive, but the details of the outburst in 2006 remain unclear.
The black hole in M31, located in the Andromeda constellation, likely continues to feed off of the stellar winds of a nearby star or the material in a large gas cloud that is falling into the black hole. As material is consumed, it drives the productions of X-rays in a relativistic jet streaming out from the black hole, which are then picked up by Chandra’s X-ray eyes.
The black hole in M31 is 10 to 100,000 times dimmer than expected, given that it has a large reservoir of gas surrounding it.
“The black holes in both Andromeda and the Milky Way are incredibly feeble. These two ‘anti-quasars’ provide special laboratories for us to study some of the dimmest type of accretion even seen onto a supermassive black hole,” Li said.
Accretion of matter into supermassive black holes is important to study because the evolution of galaxies is influenced by this process, Li said. The gravitational interplay of the black hole with the surrounding material in a galaxy, as well as the energy released when such supermassive black holes consume material in their surrounding accretion disks, change the structure of the galaxy as it forms. A better understanding of just how these supermassive black holes act in the later stages of spiral galaxy life may give clues as to what astronomers can expect to see in other galaxies.
M31 is readily seen with the naked eye in the constellation Andromeda, and is breathtaking to see through a telescope or binoculars. You won’t be able to see the black hole at its center, however! For more information on observing Andromeda, see our Guide to Space article on M31.