On Jan. 5, 2020, astrophysicists heard a chirp from a distant part of the cosmos, some 900 million light-years away. The fleeting sound was unlike any they’d heard before and was caused by a great ripple in space-time — a gravitational wave — that spread out across the universe from over 900 million light-years away, washing over the Earth and pinging detectors. Chirp.
Then, 10 days later, they heard another, similar sound. A cosmic twin. Gravitational waves had once again pinged Earth’s detectors. Chirp.
After careful analysis, the two signals have been identified as emanating from extreme, never-before-seen events in deep space: the collision between a black hole and a neutron star.
The pair of collisions (or, less poetically, “mergers”) are detailed in a new study published in the Astrophysical Journal Letters on Tuesday, featuring over 1,000 scientists from the LIGO/Virgo and KAGRA collaborations, a multinational effort to . The two newly described events are named GW200105 and GW200115, for the dates they were discovered, and provide the first definitive evidence of an elusive merger.