Illustration of the orbits of the sun-like star (blue circle) and the stellar black hole (red circle) in Gaia BH1. Note that the star and black hole are not to scale.
The star and black hole orbit each other with a period of 185.59 days and aneccentricity of 0.45. The star is similar to theSun, with about 0.93 M☉ and 0.99 R☉, and a temperature of about 5,850 K (5,580 °C; 10,070 °F), while the black hole has a mass of about 9.62 M☉.[3] Given this mass, the black hole'sSchwarzschild radius should be about 28 km (17 mi).
Artist's impression of theSun-like star(left) andblack hole(top right) in the Gaia BH1 system
Gaia BH1 was discovered in 2022 viaastrometric observations withGaia, and also observed viaradial velocity. The discovery team found no astrophysical scenario that could explain the observed motion of the G-type star, other than a black hole. The system differs from "black hole impostors" such asLB-1 andHR 6819 in that the evidence for a black hole does not depend on the mass of the star or the inclination of the orbit, and there is no evidence ofmass transfer.[3] The discovery team also found a second system that is a candidate for containing a black hole, which was also reported by another team of astronomers,[3][6] and was confirmed in 2023 asGaia BH2.[7]
The black hole was also independently detected by a second team, who found slightly different parameters.[8]
