At the hearts of most, if not all, galaxies are supermassive black holes with masses that are millions to billions of times that of the sun. For example, at the center of our galaxy, the Milky Way, lies Sagittarius A*, which is about 4.5 million solar masses in size.
A key way in which scientists think supermassive black holes grow is by engulfing stellar-mass black holes each equal in mass to a few suns. Learning how that growth process works is vital to understanding the effects they can have on the evolution of their galaxies. [Deepest-Ever X-Ray Image Captures Countless Black Holes (Photo)]
For decades, astronomers have looked for up to 20,000 black holes that previous research predicted should be concentrated around the Milky Way’s core. Sagittarius A* is surrounded by a halo of gas and dust that provides the perfect breeding ground for massive stars, which can then give rise to black holes after they die, said study lead author Chuck Hailey, co-director of the astrophysics lab at Columbia University in New York. In addition, the powerful gravitational pull of Sagittarius A* can pull in black holes from outside this halo, he added.
“The Milky Way is really the only galaxy we have where we can study how supermassive black holes interact with little ones because we simply can’t see their interactions in other galaxies,” Hailey said in a statement. “In a sense, this is the only laboratory we have to study this phenomenon.”