(Paris) – The European Gaia space telescope, dedicated to mapping the Milky Way, has discovered a black hole with a record mass of 33 times the mass of the Sun, which is unprecedented in our galaxy, according to a study published on Tuesday.
The object called Gaia BH3, which is located 2,000 light-years from Earth, in the constellation Vulture, belongs to the family of stellar black holes that result from the collapse of massive stars at the end of their lives. They are incomparably smaller than the supermassive black holes found in the hearts of galaxies, whose formation scenario is unknown.
Pasquale Panozzo, a researcher at the National Center for Scientific Research at the Paris-PSL Observatory and lead author of the work published in the journal Astronomy & Astrophysics Letters, told AFP that the discovery of Gaia BH3 was “pure coincidence.”
Scientists from the Gaia consortium were scanning the latest data from the probe, aiming to publish the next catalog in 2025, when they found a particular binary star system.
“We saw a star slightly smaller than the Sun (about 75% of its mass) and brighter, orbiting an invisible companion,” says Pasquale Panozzo, deputy head of spectroscopy. Gaia processing.
The space telescope gives the extremely precise location of stars in the sky, so astronomers were able to characterize the orbits and measure the mass of the invisible companion star: 33 times the mass of the Sun.
Further observations from ground-based telescopes confirmed that it was indeed a black hole, with a mass much greater than that of black holes of stellar origin already known in the Milky Way – between 10 and 20 solar masses.
Such giant objects have already been detected in distant galaxies, via gravitational waves. But “never in our country,” says Drs Panozzo.
Sleeping black hole
Gaia BH3 is a “dormant” black hole: it is too far away from its companion star to remove its own matter, and therefore does not emit any X-ray radiation, making it very difficult to detect.
The Gaia telescope has successfully found the first two inactive black holes (Gaia BH1 and Gaia BH2) in the Milky Way, but they have record masses.
Unlike the Sun, the small star in the BH3 binary system “contains elements heavier than hydrogen and helium,” the Paris Observatory explained in a press release.
“According to the theory, only these metal-poor stars are able to form such a massive black hole,” the doctor says.s Panozzo. Therefore, the study indicates that the “ancestor” of the black hole was a massive star that was also poor in metals.
He describes that the system's star, which is 12 billion years old, is “aging very slowly,” while the star that formed the black hole “lived only 3 million years.”
“These metal-poor stars were very present in the early days of the Galaxy. Studying them gives us information about its composition,” the scientist adds.
Another curiosity about the stellar pair is that in the disk of the Milky Way it rotates in the opposite direction to the other stars. “Maybe because the black hole formed in another, smaller galaxy, which would have eaten the Milky Way early in its life,” he suggests.
The European Space Agency's Gaia probe, which has been operating 1.5 million kilometers from Earth for 10 years, will deliver a 3D map in 2022 of the positions and movements of more than 1.8 billion D stars.
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