LIGO and Virgo detected a collision between a black hole and a mystery object
Ripples in spacetime have revealed a distant collision between a black hole and a mystery object, which appears too massive to be a neutron star but not massive enough to be a black hole. At first glance, the event — detected by the LIGO and Virgo gravitational wave detectors on August 14, 2019 — looked like a collision between a black hole and neutron star (SN: 8/15/19). But a new analysis of the gravitational waves emanating from the merger tells a different story. It shows that a black hole about 23 times as massive as the sun crashed into a compact object of about 2.6 solar masses, researchers report June 23 in the Astrophysical Journal Letters. That 2.6-solar-mass object is heavier than the presumed 2.5-solar-mass cap on neutron star size. But it’s smaller than the most lightweight black hole ever observed, which is about five solar masses. “We have [here] either the...