“It’s a runaway process,” says Frans Pretorius, of Princeton University in New Jersey. “The closer they get, the faster they spin.” Near the end, they were whirling so fast that each orbit lasted just a few milliseconds.
When they eventually merged, the single black hole that remained was 62 times the mass of the sun – three solar masses lighter than the two original black holes combined. That missing mass all went into creating gravitational waves that fluttered space-time like a sheet.
“The total power output of gravitational waves during the brief collision was 50 times greater than all of the power put out by all the of the stars in the universe put together,” said Kip Thorne of Caltech, one of LIGO’s founders. “It’s unbelievable.”