LIGO’s third detection hints at how black hole binaries are born

By Leah Crane

Three’s a party. The LIGO collaboration has made its third observation of gravitational waves emanating from a pair of merging black holes – giving us more insight into how these pairs form and building up our catalogue of them.

“The first one was a novelty. The second one was confirmation that the novelty of the first one was not a fluke. The third one is astrophysics,” says LIGO spokesperson David Shoemaker at Massachusetts Institute of Technology (MIT). “We’re making the transition to talking about a population of these objects.”

LIGO detects waveforms, which are readouts of the ripples in the fabric of the universe caused by masses moving through it. The spins of merging black holes can warp those waveforms, which are mostly produced by their orbits and eventual collision.

For the first event, we did not have enough information to determine the direction in which each black hole was spinning. For the second, we had slightly more information, indicating that each black hole was probably spinning in the same direction as they were orbiting one another.

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