The term “quasar” describes a behavior rather than an object: when a supermassive black hole (SMBH) at the center of a galaxy gorges on gas, the infalling matter produces a lot of light. While most galaxies are known to have SMBHs, not all of those exhibit quasar behavior. Similarly, black holes created from the deaths of massive stars—the stellar mass black holes—don’t generally consume matter at a rapid rate. However, a few do, and those are known as microquasars. Four microquasar candidates have been found in the Milky Way, and now one has been located in M31, the Andromeda Galaxy.

Unlike microquasars in the Milky Way, those in other galaxies potentially provide an unimpeded view of the black hole accretion process. This will allow astronomers to test whether microquasars are miniature versions of their supermassive cousins, and measure the accretion mechanism in unprecedented detail. Since the nearest “regular” quasars are much farther away than M31, a nearby microquasar provides a beautiful target for observations of how black holes beam infalling matter into jets, and the specific processes are by which they make their intense light. [Read more…]