Multiple black hole systems Binary black holes In addition, over 30 alerts have been issued since April 2019, of black hole merger candidates. In addition, one neutron star merger has been observed ( GW170817), forming a black hole. In each case two black holes merged to a larger black hole. Main article: List of gravitational wave observationsĪs of February 2019, 10 mergers of binary black holes have been observed. XTE J1650-500 (at one time considered the smallest black hole known) īlack holes detected by gravitational wave signals.MOA-2011-BLG-191/OGLE-201 (first known isolated stellar black hole).M33 X-7 (most massive stellar-mass black hole known, not counting GW black holes).LB-1 (name of both a galactic B-type star and a very closely associated over-massive stellar-mass black hole).IGR J17091-3624 (candidate smallest known stellar black hole).GRO J1655-40/ V1033 Sco (at one time considered the smallest black hole known).GRO J0422+32 (possibly the smallest black hole yet discovered).CXOU J132527.6-430023 (a candidate stellar mass black hole outside of the Local Group).A0620-00/V616 Mon (once thought to be the closest to Earth known, at about 3,000 light years).Triangulum Galaxy ( Messier 33, NGC 598).
Intermediate-mass black holes and candidates Hypercompact stellar system (hypothetical object organized around a supermassive black hole).Sagittarius A*, which is in the center of the Milky Way.RX J1131 (first black hole whose spin was directly measured).Q0906+6930 (a blazar organized around a supermassive black hole).NGC 4486B (a satellite galaxy of Messier 87).APM 08279+5255 (contains one of the largest black holes, estimated at 10-23 billion solar masses previous candidate for largest).S5 0014+81 (said to be a compact hyperluminous quasar, estimated at 40 billion solar masses).4C +37.11 (this radio galaxy is believed to have binary supermassive black holes).Ton 618 (this quasar has possibly the biggest black hole ever found, estimated at 66 billion solar masses).See also: List of most massive black holes and List of quasars