Artist’s impression of the system with the most massive stellar black hole in our galaxy. Image: ESO/L Calçada
The massive stellar black hole is far larger than any previously discovered in our galaxy, yet it is the second-closest known black hole to Earth.
Researchers have stumbled upon the most massive stellar black hole discovered yet in our Milky Way galaxy – and it is 33 times the mass of our sun.
This black hole was spotted in data from the European Space Agency’s (ESA) Gaia mission and was detected thanks to a strange ‘wobbling’ motion on the star orbiting it. But its massive size compared to other stellar black holes made the discovery a shock for the researchers.
Stellar black holes are formed from the collapse of massive stars, but the ones previously identified in the Milky Way are usually about 10 times the mass of our sun. The previous record-holder – Cygnus X-1 – is 21 times bigger than our sun in mass. The ESA described the new discovery as “exceptional”.
This newly discovered stellar black hole – dubbed Gaia BH3 – is also extremely close to us, being 2000 light-years away in the constellation Aquila. This makes it the second-closest known black hole to Earth. Further observations of this system could reveal more about its history and about the black hole itself.
“No one was expecting to find a high-mass black hole lurking nearby, undetected so far,” says Gaia collaboration member Dr Pasquale Panuzzo. “This is the kind of discovery you make once in your research life.”
To confirm the discovery, the Gaia collaboration used data from ground-based observatories, including advanced instrument on the European Southern Observatory’s (ESO) Very Large Telescope. The researchers said these observations revealed key properties of the companion star, which – combined with Gaia data – allowed the astronomers to precisely measure the mass of BH3.
Gaia was launched in 2013 to chart a three-dimensional map of the Milky Way and reveal the composition, formation and evolution of our galaxy. The researchers decided to make the data from this latest discovery available for researchers ahead of the full data Gaia release, which is planned for late 2025 at the earliest.
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