Astronomers discover the largest black hole in the Milky Way: a study

Astronomers have identified the largest stellar black hole yet discovered in the Milky Way Galaxy, with a mass 33 times the mass of the Sun, according to a study published Tuesday.

Pasquale Panozzo, an astronomer at the National Center for Scientific Research at the Paris Observatory, told AFP that the black hole, called Gaia BH3, was discovered “by chance” from data collected by the European Space Agency's Gaia mission.

Gaia, dedicated to mapping the Milky Way, is located 2,000 light-years from Earth in the Aquila constellation.

Because the Gaia telescope can pinpoint the precise location of stars in the sky, astronomers were able to determine their orbits and measure the mass of the invisible star accompanying it, 33 times the mass of the Sun.

Further observations from telescopes on Earth confirmed that it was a black hole with a mass much greater than the stellar black holes already found in the Milky Way.

“No one expected to find a high-mass black hole lurking nearby, and it has not been discovered yet. This is the kind of discovery you make once in your research life,” Panozzo said in a press release.

The stellar black hole was discovered when scientists observed an “oscillatory” movement on the companion star it was orbiting.

“We can see a star slightly smaller than the Sun (about 75% of its mass) and brighter, orbiting an invisible companion,” Panozzo said.

Stellar black holes arise from the collapse of massive stars at the end of their lives, and are smaller than supermassive black holes, whose composition is still unknown.

Such giants have already been detected in distant galaxies via gravitational waves.

“But never in our country,” Panozzo said.

BH3 is a “dormant” black hole that is too far away from its companion star to strip it of its matter, and thus does not emit any X-rays, making it difficult to detect.

The Gaia telescope has identified the first two inactive black holes (Gaia BH1 and Gaia BH2) in the Milky Way.

Gaia has been operating within 1.5 million kilometers of Earth for the past 10 years, and in 2022 provided a 3D map of the positions and movements of more than 1.8 billion stars.