Binary black hole

A Binary Black Hole (often abbreviated BBH), are two black holes in close orbit around each other. The two black holes will eventually merge into one releasing a large amount of gravitational waves.

Computer simulation of the black hole merger GW150914. The background is distorted as the intense gravity from the merger causes gravitational lensing.

Discovery

For years the existence of binary black holes was only theoretical. Proving they exist was a challenge due to the nature of black holes. Although if two black holes were to ever merge this would cause a significant amount of gravitational waves to be released. The existence of binary black holes (and gravitational waves themselves) was proven when on September 2015, LIGO detected GW150914.