The Gaia space telescope, designed by European researchers to map the Milky Way, has discovered a black hole with a record mass – 33 times that of the Sun – which is something never seen before in our galaxy, according to a published study recently, informs AFP, quoted by Agerpres.
That cosmic object, called Gaia BH3 and located 2,000 light-years away from Earth in the constellation Vulture, is part of 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 that are at the center of galaxies and whose formation scenario is unknown.
Gaia BH3 was spotted “by chance”, said Pasquale Panuzzo, a researcher at the National Center for Scientific Research (CNRS) in France working at the Paris-PSL Observatory, the lead author of the study published in Astronomy & Astrophysics Letters.
Scientists participating in the Gaia project were about to examine the latest data transmitted by the telescope, with a view to compiling a future catalog in 2025, when they discovered a special binary star system.
“We saw a star slightly smaller than the Sun (75% of its mass) and brighter, revolving around an invisible companion”, which could be detected by the disturbances it caused, explained Pasquale Panuzzo, deputy director of the spectroscopic processing department of the Gaia project.
As this space telescope establishes the very precise position of the stars in the sky, astronomers were able to characterize the orbits and measure the mass of the star’s invisible companion: 33 times that of the Sun.
More detailed observations made by 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 “mastodons” have already been detected in distant galaxies, with the help of gravitational waves. But “never in our galaxy”, said Pasquale Panuzzo.
Latent black hole
Gaia BH3 is a “dormant” black hole: it is too far from its companion star to rip off its component matter and therefore does not emit any X-rays, making its detection extremely difficult.
The Gaia telescope had already managed to discover two first inactive holes (Gaia BH1 and Gaia BH2) in the Milky Way, but they have standard masses.
Unlike the Sun, the small star in the BH3 binary system is “very poor in elements heavier than hydrogen and helium,” the Paris Observatory explained in a statement.
“According to the theory, only such metal-poor stars can form such a massive black hole,” revealed Pasquale Panuzzo. The new study therefore suggests that the “progenitor” of the black hole was a massive star that was itself poor in metals.
The star in that system, aged 12 billion years, “ages very slowly”, while the star that formed the black hole “only lived for 3 billion years”, said the coordinator of the study.
“These metal-poor stars were very present in the early galaxy. Studying them gives us information about its formation”, he added.
Another curiosity of the stellar couple: in the disk of the Milky Way, it rotates in the opposite direction to the other stars. “Maybe because the black hole would have formed in another smaller galaxy, which was ‘eaten’ at the beginning of the life of the Milky Way”, suggested Pasquale Panuzzo.
The Gaia space telescope, launched by the European Space Agency (ESA) and operating for 10 years at 1.5 million kilometers from Earth, provided in 2022 a 3D map of the positions and movements of more than 1.8 billion stars.
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Tags: atypical black hole Milky discovered researchers European space telescope Gaia
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