GW190521 (initially S190521g) was a gravitational wave signal resulting from the merger of two black holes. It was possibly associated with a coincident flash of light; if this association is correct, the merger would have occurred near a third supermassive black hole. The event was observed by the LIGO and Virgo detectors on 21 May 2019 at 03:02:29 UTC, and published on 2 September 2020. The event was 17 billion light years away from Earth, within a 765 deg2 area towards Coma Berenices, Canes Venatici, or Phoenix. At 85 and 66 solar masses (M☉) respectively, the two black holes comprising this merger are the largest progenitor masses observed to date. The resulting black hole had a mass equivalent to 142 times that of the Sun, making this the first clear detection of an intermediate-mass black hole. The remaining 9 solar masses were radiated as energy in the form of gravitational waves. From Wikipedia
