Black holes are everywhere. There could be a hundred million black holes that are the remnants of dead stars in the Milky Way Galaxy alone. But because they’re completely dark, they’re hard to find. That applies even to the biggest member of the class yet discovered. It’s 33 times the mass of the Sun – more than half again the mass of the galaxy’s previous record holder.

The black hole is in a system known as BH3. It was discovered by the Gaia space telescope, which is mapping more than a billion stars in the galaxy. The system is almost 2,000 light-years from Earth.

The black hole revealed its presence only because it has a “normal” companion star. The companion is nearing the end of its life, so it’s becoming a giant – bigger and brighter than the Sun.

Gaia measured a wobble in the star’s motion. Astronomers analyzed the wobble, and decided that it was caused by the gravitational pull of a black hole.

The black hole probably formed when a supergiant star collapsed at the end of its life. That happened billions of years ago, when the galaxy was young – a conclusion supported by the age of the companion. The composition of the supergiant allowed it to form an especially heavy black hole – the biggest remnant black hole in the galaxy.

BH3 is to the left of the bright star Altair, the breast of the eagle, which is in the east at nightfall. But the system is much too faint to see without a big telescope.

Script by Damond Benningfield