Artist's Rendition of a Mystery Object in 'Mass Gap' Found by LIGO and Virgo

In August of 2019, the LIGO-Virgo gravitational-wave network witnessed the merger of a black hole with 23 times the mass of our sun and a mystery object 2.6 times the mass of the sun. Scientists do not know if the mystery object was a neutron star or black hole, but either way it set a record as being either the heaviest known neutron star or the lightest known black hole. Image credit: LIGO/Caltech/MIT/R. Hurt (IPAC)