'Traffic jams' in the hearts of galaxies can force black holes to collide
Supermassive black holes may create conditions akin to "cosmic intersections with failed traffic lights" that make collisions between smaller stellar-mass black holes inevitable.
Evgeni Grishin Monthly Notices Of The Royal Astronomical Society Monash University Monash University School Of Physics Active Galactic Nucleus Monash University School
Source: yahoo.com