Black Holes Form Binary Systems When Galaxies Collide

When two gas-rich galaxies collide, their black holes usually capture each other in a binary system less than a billion years later, according to simulations by Stelios Kazandzidis from the Kavli Institute for Particle Astrophysics and Cosmology in California.

Most large galaxies contain a black hole millions of times as massive as the Sun.  Astronomers have shown that supermasive black holes are common even in galaxies in regions of the Universe where there is scarcely any matter.