LIGO and Virgo probably spotted the first black hole swallowing up a neutron star

Shudders in the cosmos have revealed what’s likely the sad end of a neutron star — getting swallowed by a black hole.

If confirmed, it would be the first solid detection of this source of gravitational waves, revealing a type of cataclysm never before spotted. Researchers from the LIGO and Virgo gravitational wave observatories reported the candidate event, which was detected August 14, in a public database used by astronomers.

Scientists are still analyzing the data to verify what created the gravitational waves, which are tiny vibrations in spacetime caused by massive, accelerating objects. But one thing seems fairly certain: “Something has occurred out there in the sky,” says physicist Daniel Holz of the University of Chicago, a member of LIGO. “So far, it doesn’t obviously look like anything we’ve detected with high confidence before.”

LIGO and Virgo previously have picked up gravitational waves from pairs of merging black holes and from colliding neutron stars, which are extremely dense collapsed stars (SN: 1/19/19, p. 10). In April, scientists saw tentative hints of a rendezvous between a black hole and neutron star, but the signal was weak and could have been a false alarm (SN Online: 5/2/19).

This new discovery offers much more solid evidence: The detection was so clear that it’s considered very unlikely to be a false alarm. The researchers estimate that the run-in between the two objects occurred around 900 million light-years away, and within an area about 23 square degrees across the sky. (For comparison, the moon is about half a degree across.) Astronomers have since been peering at that region with their telescopes, looking for any light that may have been emitted in the merger. Such light could have been released if the neutron star were torn apart by the black hole before being gulped within its depths.

Further study of the encounter could help reveal new secrets about some of the universe’s most mysterious objects. But the potential detection is exciting on its own, Holz says. “The first of anything is always really fascinating.”