A team of scientists, including astronomers from the University of Geneva (UNIGE), has found a massive “dormant” black hole just 2,000 light-years from Earth. This is the first time a black hole of this size has been detected so close to our planet.
The black hole, dubbed Gaia BH3, has a staggering mass of almost 33 times that of our Sun. It was detected thanks to highly precise data from the European Space Agency’s Gaia mission, which is mapping the positions and motions of over a billion stars.
The quality of the latest data produced by the Gaia consortium has improved so much that we expect to publish a good number of genuine black holes in the upcoming Gaia Data Release 4 catalog, said Berry Holl, a senior research associate at the UNIGE Department of Astronomy and a co-author of the study published in Astronomy and Astrophysics.
The discovery challenges our understanding of how massive stars evolve. Typically, black holes of stellar origin are around 10 times the mass of the Sun. The previous record holder, Cygnus X-1, was estimated to be about 20 times the Sun’s mass.
The discovery of Gaia BH3 within our Galaxy is a unique opportunity to study the environment in which these unexpectedly massive stellar black holes reside and understand their origin, said Nami Mowlavi, a principal investigator at the UNIGE Department of Astronomy and a co-author of the paper.
The black hole’s companion is an unusual old giant star from the galactic halo, moving in the opposite direction to the stars in the galactic disk. This suggests the progenitor of Gaia BH3 could have been a massive, metal-poor star, which may have evolved differently from the stars we see in the Milky Way’s disk and near the Sun.
This supports, for the first time, the idea that the high-mass black holes observed in gravitational wave experiments were produced by the collapse of primordial metal-poor massive stars, the researchers explained.
These early, metal-poor stars may have retained most of their mass until the end and, once the nuclear fuel in their cores was exhausted, collapsed to form the massive black holes we see today.
The Gaia team found this treasure while validating the preliminary data for the upcoming Gaia Data Release 4, which is not expected to be published until at least late 2025. However, the significance of the discovery prompted the team to announce it before the official data release.
I am very pleased to be able to share this amazing discovery with everyone, said Laurent Eyer, an associate professor at the UNIGE Department of Astronomy and a co-author of the study. Now that scientists’ curiosity has been piqued, this black hole and its companion will undoubtedly be the subject of many in-depth studies in the future.
Sources
Université de Genève | European Southern Observatory | Gaia Collaboration: P. Panuzzo, T. Mazeh, et al., Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry. Astronomy & Astrophysics. doi.org/10.1051/0004-6361/202449763
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