Scientists discover the largest stellar black hole in the Milky Way

Published on 16 April 2024

A European team of astronomers has discovered the largest stellar black hole in the Milky Way. It is more than thirty times as massive as our sun and is located in the constellation of Aquila, about two thousand light-years from Earth. The astronomers stumbled upon the black hole by chance while preparing the fourth data release from ESA’s Gaia mission, which tracks the movements of billions of stars in the Milky Way.

The black hole was noticed because it induces a peculiar ‘wobble’ in the star orbiting it. The researchers used data from the European Southern Observatory’s Very Large Telescope (VLT) to confirm the mass of the black hole. Among those involved from the Netherlands are Anthony Brown, Amina Helmi, and Eduardo Balbinot.

Artist's impression of the star system with the heaviest stellar black hole in our Milky Way galaxy. Astronomers have discovered the heaviest black hole in our Milky Way galaxy, thanks to the wobbling motion it induces in an accompanying star. This artist's impression shows the orbits of both the star and the black hole, named Gaia BH3, around their common center of mass. The wobbling motion has been measured over multiple years with the Gaia space telescope of the European Space Agency (ESA). Additional data from other telescopes, including ESO's Very Large Telescope in Chile, have confirmed that the mass of this black hole is 33 times that of our sun. (c) ESO/L. Calçada

‘This news had to be shared right away'

Anthony Brown (Leiden University) heads the Data Processing and Analysis Consortium of Gaia. He leads the preparation of the data releases. ‘The fourth data release is scheduled for late 2025. While preparing the data, we often come across remarkable things, but this was so surprising that we decided to announce it now. This way, scientists worldwide can investigate this extraordinary black hole as soon as possible.’

Captured by the Milky Way?

Amina Helmi (University of Groningen) is involved in the discovery as a member of the Data Processing and Analysis Consortium of Gaia and because of her expertise in old stars and stellar streams. ‘Thanks to that orbiting star, we were able to discover the black hole. The star, and the black hole, appear to originate from a group of stars that have been captured by our Milky Way, which was previously discovered by my own research group. I had been looking at that group of stars for a while, coincidentally. And now, it turns out there is a black hole present, which is very special. We have never seen a stellar stream with a black hole before.’

Direct all telescopes to the black hole, please

Eduardo Balbinot (University of Groningen and Leiden University) is also a member of the Data Processing and Analysis Consortium of Gaia and specialises in preparing and processing large amounts of data about stars. Like Helmi, he searches for stellar streams that have been captured by our Milky Way over billions of years. ‘We hope that thanks to new spectroscopic observations, we will soon learn more about the origin of the stellar stream and about the black hole. And I assume that many telescopes will now be prioritising observations of the star and the black hole.’

Further reading

Read more in the ESO press release.

Read the scientific paper in Astronomy & Astrophysics: Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry. Door: Gaia Collaboration, P. Panuzzo, et al.