SAN DIEGO — While astrophysicists celebrate the second detection of ripples in spacetime (SN Online: 6/15/16), they are also looking ahead to figuring out what led to these cosmic quakes. Black holes colliding in remote galaxies sent the gravitational waves our way. But how these duos ended up in an ill-fated embrace in the first place is unknown.
With only two clear detections from the Advanced Laser Interferometer Gravitational-Wave Observatory, and a third marginal candidate, there isn’t enough information to figure out for sure how these binary black holes formed. But there are two leading ideas.