The black hole, known as Gaia BH3, is 33 times the mass of our Sun and located relatively close to Earth at 2,000 light years away. (The Milky Way is 100,000 light years across.)
The only black hole known to be more massive in our galaxy is the supermassive black hole at its centre which could not have been born from the collapse of a single exploding star and whose formation is tied to the formation of the Milky Way itself.
Gaia BH3 was not seen directly but inferred from the movements of what appeared to be a lone star now understood to be the black hole’s companion, i.e., gravitationally bound to the black hole and orbiting around a common point.
Most known black holes are active – that is, they gobble matter from a nearby star companion. Gaia BH3 is a dormant black hole as it does not have a companion close enough to steal matter from and does not generate any light. It is therefore much harder to spot.
Currently, there are about 50 confirmed or suspected black holes in our galaxy, but theory predicts there is a hidden population of thousands or millions, due to the number of stars that have likely already died over the galaxy’s lifetime.
Dr George Seabroke (Mullard Space Science Laboratory at UCL), a member of Gaia’s Black Hole Task Force, the team that made the discovery, said: “Finding Gaia BH3 is like the moment in the film The Matrix where Neo starts to ‘see’ the matrix. In our case, ‘the matrix’ is our galaxy’s population of dormant stellar black holes, which were hidden from us before Gaia detected them.