Milky Way’s most massive stellar black hole discovered

Astronomers have discovered the most massive black object ever found in the Milky Way. The object, named Gaia BH3, or BH3, is located just 1,924 light-years from the solar system in the constellation of Aquila. The study was published in the journal Astronomy & Astrophysics.

Stellar-mass black holes form when massive stars collapse at the end of their life cycle. BH3 has a mass of 33 solar masses, making it the most massive known stellar-mass black hole.

BH3 poses no threat to Earth because its gravitational field is no stronger than that of a star of equivalent mass. However, the discovery of BH3 raises questions about how many more stellar-mass black holes are lurking in the Milky Way.

“No one expected to find a large mass black hole lurking nearby,” said astronomer Pasquale Panuzzo of the National Center for Scientific Research (CNRS) in France. “You make such a discovery once in your research life.”

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BH3 was discovered using the Gaia spacecraft, which maps the three-dimensional positions and movements of stars in the Milky Way. Gaia discovered that BH3 is in a binary orbit with a companion star whose motion cannot be explained in any way other than the presence of a black hole.

The companion star has a mass of 0.76 solar masses and contains very few heavy elements. This indicates that the star is very old. The star also shows no signs of contamination by material that the black hole’s predecessor must have ejected when it went supernova. This suggests that BH3 and its companion star converged on their “orbital dance” after the black hole had already formed.

The discovery of BH3 is an important step in understanding stellar mass black holes. It also indicates that there may be many more stellar-mass black holes in the Milky Way than we previously thought.

“We have taken the extraordinary step of publishing this paper based on preliminary data ahead of the upcoming release of Gaia due to the unique nature of the discovery,” said astronomer Elisabetta Caffau of CNRS.