Stellar-Mass Population Estimate

The Milky Way alone may contain 100 million stellar-mass black holes, the remnants of massive stars that have died over the galaxy's 13-billion-year history. Most are solitary and completely invisible, drifting through interstellar space with no nearby matter to give them away.

Occasionally, a wandering black hole passes in front of a distant star, bending its light through gravitational microlensing. In 2022, astronomers used this technique to detect an isolated black hole for the first time — a dark object of about 7 solar masses located 5,000 light-years away.