Gaia mission detects largest known stellar black hole

According to a study published on Tuesday, astronomers have discovered the largest stellar black hole ever identified in the Milky Way, with a mass 33 times that of the sun.

The black hole, named Gaia BH3, was discovered “by chance” from data collected by the European Space Agency’s Gaia mission, an astronomer from the National Center for Scientific Research (CNRS) at the Observatoire de Paris, Pasquale Panuzzo, told Agence France-Presse (AFP).

Gaia, dedicated to mapping the Milky Way galaxy, is located BH3 2,000 light years away from Earth in the Aquila constellation.

As Gaia’s telescope can precisely position stars in the sky, astronomers could characterize their orbits and measure the mass of the star’s invisible companion – 33 times that of the sun.

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

“No one was expecting to find a high-mass black hole lurking nearby, undetected so far. This is the kind of discovery you make once in your research life,” Panuzzo said in a press release.

Scientists discovered the stellar black hole when they spotted a “wobbling” motion in the companion star orbiting it.

“We could see a star a little smaller than the sun (around 75% of its mass) and brighter that revolved around an invisible companion,” Panuzzo said.

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

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

But “never in ours,” said Panuzzo.

BH3 is a “dormant” black hole too far away from its companion star to strip it of its matter. Therefore, it emits no X-rays, making it difficult to detect.

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

For the past 10 years, Gaia has been operating 1.5 million kilometers (over 930,000 miles) from Earth and delivered a 3D map of the positions and motions of more than 1.8 billion stars in 2022.