Gaia BH3: A 'Sleeping Giant' Black Hole Discovered in Our Galaxy
October 1, 2025
Astronomers have discovered Gaia BH3, the Milky Way's most massive stellar black hole. This 'sleeping giant' weighs 33 solar masses, challenging our understanding.
In a groundbreaking discovery, astronomers using data from the European Space Agency's Gaia mission have identified Gaia BH3, the most massive stellar black hole yet found in the Milky Way. Weighing in at an astounding 33 times the mass of our Sun, this 'sleeping giant' was hiding in plain sight, just 2,000 light-years away in the constellation Aquila, making it the second-closest known black hole to Earth.
An Accidental Cosmic Find
The detection of Gaia BH3 was a complete surprise. Unlike most black holes, which are found by the X-rays emitted as they devour material from a companion star, Gaia BH3 is dormant. It was discovered indirectly by observing a peculiar 'wobble' in the motion of its companion star. This gravitational dance revealed the presence of a massive, invisible object, a discovery that the Gaia collaboration was not actively searching for, making it a true moment of serendipity.
What Makes Gaia BH3 So Special?
- Record-Breaking Mass: At 33 solar masses, its size far exceeds other known stellar black holes in our galaxy, which average around 10 solar masses. This challenges current models of how massive stars evolve and die.
- Stellar Origins: Gaia BH3 is believed to have formed from the collapse of a massive star. Its companion is a very old, 'metal-poor' star, suggesting the black hole's progenitor star was also low in heavy elements, a key clue to its formation.
- A Dormant Giant: As a 'sleeping' black hole, it does not emit X-rays, making it incredibly difficult to find. This discovery suggests there could be a large, hidden population of similar dormant black holes throughout the Milky Way.
This is the kind of discovery you make once in a research life. So far, black holes of this mass have only ever been detected in distant galaxies, with LIGO. To find one so close is exceptional.
The discovery of Gaia BH3 opens up a new avenue for understanding the life cycle of massive stars and the formation of black holes. Its unique characteristics provide a pristine laboratory for testing theories of stellar evolution and gravitational physics. Further observations with ground-based telescopes are already confirming its properties, heralding a new chapter in the exploration of our galactic neighborhood.
Gaia BH3: A 'Sleeping Giant' Black Hole Discovered in Our Galaxy - FAQs
Gaia BH3 is the most massive stellar black hole discovered to date in the Milky Way galaxy, boasting a mass approximately 33 times that of our Sun.
It's called a 'sleeping' or 'dormant' black hole because it isn't actively consuming material from its companion star, meaning it doesn't emit detectable X-rays, which makes it much harder to find.
It was discovered by the ESA's Gaia space telescope, which detected an unusual wobble in the motion of a star, revealing the gravitational pull of a massive, unseen companion object—Gaia BH3.
Gaia BH3 is located relatively close in cosmic terms, at just 2,000 light-years away from Earth in the constellation Aquila, making it the second-closest known black hole.