GW190521 (or GW190521g; initially, S190521g)[1] is a gravitational wave signal resulting from the merger of two black holes near a third supermassive black hole, which was associated with a coincident and uncharacteristic flash of light.[2][6] The event was observed by the LIGO and Virgo detectors on 21 May 2019 at 03:02:29 UTC,[7] and later confirmed in studies published on 2 September 2020.[5][5][6] The event was located 17 billion light years away,[n 1][5][7] in location area 765[10] deg2[n 2][11][12] towards Coma Berenices, Canes Venatici, or Phoenix.[1][2][6][13]