Stellar black hole more massive than the Milky Way discovered

Astronomers have discovered a black hole of stellar origin, dormant and massive. One of a kind, it is the first to combine these characteristics and whose discovery was possible thanks to the mission Gaia of the European Space Agency (ESA). “I never expected to find such a massive black hole, so close to our home,” said professor Pasquale Panuzzo to Average Inaf Calabrian engineer, main author of the study published on Astronomy and Astrophysics Letters.

The stellar black hole Gaia BH3

The study published in the journal Astronomy and Astrophysics Letters, in which several INAF researchers took part (National Institute of Astrophysics), accurately describes the new discovery: a black hole of stellar origin that stands out due to its characteristics, above all its “weight”. It is, in fact, the more massive than our Galaxy.

Thanks to the data analyzed, on all those of the Very Large Telescope from the European Southern Observatory (VLT) and other ground-based observatories, the team of astronomers was able to ascertain that the mass of this black hole – called Gaia BH3 – is 33 times that of the sun. Like all black holes of stellar origin, Bh3 it formed from the collapse of a massive star but unlike those identified so far in the Milky Way, it is extremely close to Earth: in fact, it is located just 2,000 light years away in the Constellation of Aquila.

“No one expected to find a high-mass black hole lurking nearby, so far undetected,” said professor Pasquale Panuzzo, astronomer of the National Center for Scientific Research (CNRS) at the Paris Observatory -. This is the kind of discovery you make once in your research life.”

One of the adjectives that astronomers have used to describe Gaia BH3 is “sleepy”. It means that this black hole does not emit radiation like “active” ones do and that it essentially does not take mass from nearby celestial bodies. Data analysis allowed astronomers to learn more about BH3’s “companion” star and the one that collapsed to form the black hole, concluding that it is very poor in metals.

The latest and most important discoveries about black holes

“Black holes of this mass have been observed with gravitational waves in external galaxies, but i stellar evolution models fail to explain them, unless we assume that they are formed by massive stars with low metallicity – explained Panuzzo to Inaf -. Our black hole is therefore the first discovered in our galaxy equivalent to the high-mass black holes observed with gravitational waves. Furthermore, the fact that it has a low metallicity star as a companion tells us that it was too formed by a low metallicity star. This discovery is therefore the first confirmation of those models that explain the high-mass black holes seen with gravitational waves as due to low metallicity stars.”

I study still needs to delve deeper into some aspects, above all the process that led to the formation of this black hole-star binary system with a wide orbit. “We took the exceptional step of publishing this paper based on preliminary data before the imminent release of Gaia due to the unique nature of the discovery,” added one of the study’s authors, Elisabetta Caffau, also a member of the Gaia collaboration and a scientist of the CNRS of the Paris Observatory.

Recall that Gaia BH3 is the most massive black hole of stellar origin in the Milky Way, but the record goes to Sagittarius A, a supermassive black hole located at the center of our Galaxy with a mass about four million times that of the Sun.