High Quality Content by WIKIPEDIA articles! A binary black hole is two black holes in close orbit around each other. Although only a theoretical idea, they are important in astrophysics in that they would be the strongest known gravitational wave source in the universe. As the orbiting black holes give off these waves, the orbit decays, and the orbital period decreases. This stage is called binary black hole inspiral. The black holes will merge once they are close enough. Once merged the single hole goes through a stage called ring down where any distortion in the shape is dissipated as more gravitational waves.