Black hole with record mass is discovered in the Milky Way – 04/16/2024 – Science

The European Gaia space telescope, dedicated to mapping the Milky Way, led to the discovery of a black hole whose mass is 33 times that of the Sun. This is something never seen in our galaxy, according to a study published this Tuesday (16).

The object, named Gaia BH3 and located 2,000 light years from Earth, in the Eagle constellation, belongs to the family of stellar black holes that arise from the collision of massive dead stars.

They are much smaller than the massive black holes located in the hearts of galaxies, whose formation process is unknown.

The discovery of Gaia BH3 happened “by chance”, Pasquale Panuzzo, researcher at the CNRS institute at the Paris-PSL Observatory and main author of the work published in Astronomy & Astrophysics Letters, told AFP.

Scientists from the Gaia consortium were analyzing the probe’s latest data, with the aim of publishing the next catalog in 2025, when they found a specific binary star system.

“We saw a star a little smaller than the Sun (75% of its mass) and brighter, which was rotating around an invisible companion”, which could be inferred from the disturbances it caused, said Panuzzo, deputy responsible for the spectroscopic treatment of Gaia.

The space telescope gives the precise position of the stars in the sky and astronomers were able to categorize the orbits and measure the mass of the star’s invisible companion: 33 times that of the Sun.

More advanced observations from ground-based telescopes confirmed that it was 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.

These giants have already been detected in distant galaxies, using gravitational waves. But never in ours, according to Panuzzo.

Dormant black hole

Gaia BH3 is a “sleeping” black hole: it is too far from its companion star to take matter from it and therefore does not emit any X-rays, which makes its detection very difficult.

The Gaia telescope managed to discover the first two inactive black holes (Gaia BH1 and Gaia BH2) in the Milky Way, but these 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 theory, only metal-poor stars can form a black hole of such massive mass”, points out Panuzzo. The study therefore suggests that the “progenitor” of the black hole was a massive star also poor in metals.

The system’s 12-billion-year-old star ages very slowly, while the one that formed the black hole only lived for 3 million years, he adds.

“These metal-poor stars were very present at the beginning of the galaxy. Their study gives us information about their formation.”

Another curiosity about the stellar couple is that the Milky Way’s disk rotates in the opposite direction to that of the other stars. “Perhaps because the black hole formed in another smaller galaxy that was devoured early in the Milky Way’s life,” he adds.

The ESA (European Space Agency) Gaia probe, which has been operating 1.5 million kilometers from Earth for 10 years, provided in 2022 a third-dimensional map of the positions and movements of more than 1.8 billion stars.