Astrophysicists believe there are tens of thousands of black holes near the center of our galaxy. This hypothesis is based on the likely discovery of a dozen smaller black holes surrounding the massive black hole at the center of the Milky Way: Sagittarius A.
The astronomers have found evidence for the presence of a dozen black holes around Sagittarius A by looking for less bright, but more consistent X-rays produced by the merger of an X-ray binary. The binary star system is in an inactive state. The astronomers specifically looked for the bond between a black hole and a star with a relatively low mass, because the radiation is more consistent from these binary stars than from binary stars with more massive stars. In their search, scientists at Columbia University used archival data from NASA’s Chandra X-ray Observatory. Based on the data, twelve have been found that are within three light years of Sagittarius A.
The discovery confirms a decades-old theory that there must be thousands of black holes surrounding supermassive black holes, the scientists say. By extrapolating the results from analyzes of where such already discovered binary star systems are located in space, the scientists argue that there must be between 300 and 500 X-ray binaries with relatively low mass stars in the same vicinity of the 12 discovered binaries. , along with ten thousand black holes.
Until now, scientists have mainly searched for these black holes by looking at the bright X-rays emitted when such a black hole binds, as it were, to a passing star, forming an X-ray binary. This process releases a significant amount of X-rays. According to the researchers, this has yielded little, because the center of the Milky Way is so far away that such radiation is only strong and bright enough once every hundred or thousand years. In addition, searching for individual black holes is difficult because they are only black and show little activity.
According to the astronomers, their research could be of great significance for gravitational wave research, because it is important for research in this field to know how many black holes are located at the center of an average galaxy. Possibly it will be possible to better predict how many gravitational waves can be associated with black holes. The research is published in the scientific journal Nature, under the title ‘A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy’.