For the first time, researchers have confirmed the detection of a collision between a black hole and a neutron star. Even more impressive than confirming the first such collision is that the scientists detected two events occurring only ten days apart in January 2020. The mergers sent gravitational waves rippling across 900 million light-years to reach Earth.
Scientists say that in each case, the neutron star was likely swallowed whole by its blackhole partner. A gravitational wave is a disturbance in the curvature of space-time created by massive objects in motion. The first time a gravitational wave was measured was five years ago, and the scientists who measured the wave won the 2017 Nobel Prize in physics. Since that first measurement, researchers have been able to identify more than 50 gravitational wave signals created from the merging of pairs of black holes and pairs of neutron stars.
Both black holes and neutron stars are the remnants of the death of massive stars, with black holes being the most massive of the two. The new study confirms the detection of gravitational waves in two rare events that both involve the collision of a black hole with a neutron star. The gravitational waves were detected by the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory in the US and by the Virgo detector based in Italy.
There is a third detector that’s part of the LIGO-Virgo network based in Japan called KAGRA, but that device wasn’t online during the events. Caltech researcher Ryan Magee says scientists suspected systems such as these existed but had been unable to find any until now. The first merger was detected on January 5, 2020, and involved a black hole approximately nine times the mass of the sun and a 1.9 solar mass neutron star.
The second merger was detected on January 15 and involved a six-solar-mass blackhole and a 1.5-solar-mass neutron star. The signal indicating the merger was strong in only one detector, so the merger’s location in the sky is uncertain. Both mergers happened outside of our galaxy, but scientists have been searching the Milky Way for decades trying to find a neutron star orbiting a black hole.