A record-breaking black hole was hiding in the Milky Way just 2,000 light years away and had so far gone unnoticed: it is the most massive black hole in our galaxy born from the collapse of a star, with a mass that is 33 times greater than that of the Sun, and was identified thanks to data collected by the Gaia mission of the European Space Agency. The discovery, published in the journal Astronomy and Astrophysics, was led by the French national center for scientific research, the CNRS, and also saw the collaboration of the National Institute of Astrophysics, the Italian Space Agency, the universities of Catania, Turin and Padua and the International School of Advanced Studies in Trieste.
Previously identified black holes of this type in the Milky Way are on average about 10 times more massive than the Sun, and even the second largest known, called Cygnus X-1, reaches only 21 solar masses, making this new discovery exceptional. “No one expected to find a black hole of such high mass lurking nearby, so far undetected,” comments Italian Pasquale Panuzzo of the CNRS, who led the study: “This is the kind of discovery you make once in a lifetime. your life as a researcher”.
The observation was then confirmed by several ground-based telescopes, including the Very large telescope of the European Southern Observatory in Chile, which also made it possible to reveal several key features of the companion star of the black hole, called ‘Gaia BH3’. Paired stars, in fact, tend to have similar compositions, and therefore the composition of one also provides important information about the other. The data shows that the companion is very poor in heavy metals, confirming the theory that these very massive black holes form from metal-poor stars, which lose less mass during their lifetime and therefore have more material left over when they die. .
