The brightest objects in the universe have massive black holes at their hearts.
Quasars (“quasi-stellar radio sources”) can be brighter than entire galaxies, and they’re thought to be fueled by the friction and heat of stuff that’s getting swallowed up by a black hole. (Although light can’t escape a black hole, it can escape from the event horizon—the boundary and point-of-no-return surrounding the black hole.)
Now, it turns out that the quasar nearest to Earth, located 600 million light-years away in a galaxy called Markarian 231, is actually built around two twirling black holes. It’s a first-of-its-kind type of find, and scientists think there could be a lot more quasars with binary hearts out there.
Hubble data revealed a mysterious hole in the quasar’s accretion disk, or the ring of gas that spirals around the black hole, waiting to fall in. After doing some modeling studies, scientists concluded that the system must be made of two black holes: a large one and a small one orbiting each other.
Source: Scientists Find A Double Black Hole Inside A Nearby Quasar | Popular Science