How dancing black holes get close enough to merge
The numerous black hole mergers discovered by gravitational wave observatories show that black holes collide far more often than previously believed. Black holes can now merge swiftly, according to new study, if they are trapped in the accretion disk of a supermassive partner. Astrophysically speaking, it is not difficult to bring two black holes together. They either randomly come across one another in the depths of interstellar space, or they are born that way as the children of a binary star system. They can continue to circle each other indefinitely once in orbit. Astronomers were aware that binary orbiting black holes inevitably met their demise even before the gravitational waves from merging black holes were discovered. We are aware that practically every galaxy in the cosmos has a massive black hole at its heart and that enormous galaxies form as a result of several smaller galaxies joining together. However, most galaxies only have one massive black hole, which suggests that i...