Gaia BH1

A black hole with no bright disc

Most known stellar-mass black holes reveal themselves by pulling gas from a companion and glowing brightly in X-rays. Gaia BH1 is different: it is dormant, with no luminous accretion disc, and was found through the gravitational motion it imposes on its companion.

The companion is a Sun-like star orbiting the unseen black hole every 186 days at a separation comparable to Earth's distance from the Sun. The star's wobble in the sky was measured by the Gaia mission, then confirmed with spectroscopic follow-up.

Why dormant black holes matter

If black holes are usually quiet, X-ray surveys will miss most of them. Astrometric searches like Gaia's can find them by their gravitational influence alone, revealing a population that was previously hidden.

Gaia BH1 is a benchmark for understanding how massive stars collapse and how binary systems survive the explosion that creates a black hole.

Close, but not visible

At about 1,560 light-years, Gaia BH1 is a near neighbour on the scale of the Galaxy, yet it emits no detectable light of its own. Its existence is inferred from the orbit of a star we can see.