Biggest black hole collision yet detected by gravitational waves

Some 9 billion years ago, a pair of black holes — around 51 and 34 times the mass of the Sun — merged in a colossal collision.  They formed a new black hole around 80 times the mass of the Sun, and the ensuing blast in their final seconds sent gravitational waves coursing through space-time.  Travelling at the speed of light, those infinitesimally tiny ripples washed through Earth on July 29 last year.