Multiple mergers may create pairs that coalesce to make gravitational waves
WASHINGTON — Researchers have devised a test to see if pairs of black holes — famous for creating gravitational waves when they merge — themselves formed from multiple mergers of smaller black holes.
The Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, has detected spacetime ripples from two sets of merging black holes (SN: 7/9/16, p. 8). Scientists typically assume that such black holes formed in the collapse of a massive star. But in especially crowded patches of the universe, black holes could have formed over generations of unions, astrophysicist Maya Fishbach of the University of Chicago explained January 28 at a meeting of the American Physical Society. Or the merging cycle could have occurred in the very early universe, starting with primordial black