Astronomers have discovered the most massive black object ever found in the Milky Way. The object, called Gaia BH3 or BH3, is located just 1,924 light-years from the solar system in the constellation Aquila. The research was published in the journal Astronomy and astrophysics.
Stellar-mass black holes form when massive stars collapse at the end of their life cycles. BH3 has a mass of 33 solar masses, making it the heaviest known black hole with stellar mass.
BH3 poses no threat to Earth because its gravitational field is no stronger than that of a star of the same mass. However, the discovery of BH3 raises questions about how many more stellar-mass black holes are lurking in the Milky Way.
“Nobody expected a big black hole to be lurking nearby,” says astronomer Pasquale Panuzzo of the National Center for Scientific Research (CNRS) in France. “You make a discovery like that once in your research life.”
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 became a supernova. This suggests that BH3 and its companion star came together during 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 took 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 CNRS astronomer Elisabetta Caffau.
