Scientists from the University of California in Irvine (USA) estimated the number of black holes in the Milky Way.
In the Milky Way, scientists have counted several million black holes, which are about thirty times heavier than the Sun.
The authors came to their conclusions using the observed relationship between the mass of the Galaxy and stellar metallicity (the content of elements heavier than helium).
Scientists note that the smaller the galaxy, the greater the proportion of black holes in it, which are 50 times heavier than the Sun. On the other hand, the proportion of black holes that are ten times heavier than light is large in large stellar systems.
Approximately one percent of black holes are binary systems. They are, they note, of interest to the gravitational-wave observatory LIGO (Laser Interferometric Gravitational Observatory), which September 14, 2015, for the first time observed the perturbations of space-time.