Thanks to the Gaia mission, the European Space Agency's (ESA) most ambitious project to detail the stellar mapping of our galaxy, a massive stellar black hole, Gaia BH3, has been discovered in the Milky Way. This type of black hole has been found before in distant galaxies by gravitational-wave observations, and is now identified for the first time in our galaxy. It is a dormant black hole, is the second closest to Earth - at a distance of 590 pc (or 1926 light-years) - is about thirty-three solar masses and forms a large binary system with its companion star.
This exceptional discovery confirms some theories and needs revision as well. This is an exciting result for the astronomical community, which raises the question of how many such black holes there are in space, or what mass ranges of black holes the Gaia mission will be able to discover.
This finding, published in the prestigious journal Astronomy & Astrophysics, involved a team of astronomers and engineers from the Department of Quantum Physics and Astrophysics, the Institute of Cosmos Sciences (ICCUB) of the University of Barcelona and the Institute of Space Studies of Catalonia (IEEC), who have been part of the Gaia mission, the most ambitious project of the European Space Agency (ESA) to study the history and structure of the Milky Way.
How can a dormant black hole be detected?
If the black hole is dormant, doesn't that make it hard to spot it? Most known black holes are detected through the X-rays they emit when material from their stellar companion is "eaten". With dormant black holes, little or no radiation is emitted by the source, so the black hole can only really be seen because of the gravitational effect it exerts on its companion star. Dormant black holes had never been detected before the Gaia mission. In particular, after the release of the third Gaia data release - the Gaia Data Release (DR3) - the first dormant black holes in our galaxy could be identified: Gaia BH1 and Gaia BH2.
"This is the kind of discovery you make once in your research life. So far, black holes this big have only ever been detected in distant galaxies by the LIGO-Virgo-KAGRA collaboration, thanks to observations of gravitational waves", says expert Pasquale Panuzzo, from the Paris Observatory of the Centre National de la Recherche Scientifique (CNRS) in France, and lead author of the paper.
