Top 10 Black Holes

When stars undergo nuclear fusion, it exerts an outward pressure that counteracts the force of gravity trying to push the star inward.

When a very massive star runs out of the fuel it needs for nuclear fusion, it can no longer maintain that pressure and goes supernova, spewing out its outer layers as the remaining core collapses into the most extreme type of object in the universe: a black hole.

A black hole is a point of no return, and once something crosses the event horizon, it can never go back. So far, we've discovered hundreds of black holes, and it's estimated that 100 million may lurk in the Milky Way alone.

1. Sagittarius A*

   

   Sagittarius A* is a supermassive black hole of 4.2 million solar masses in the center of the Milky Way galaxy.

2. Messier 87*

   

   Messier 87* is a very massive supermassive black hole, estimated to be 6 billion times the mass of our Sun. It was the first black hole to be directly imaged by humans.

3. Cygnus X-1

   Cygnus X-1 is a 29-solar-mass stellar black hole in a binary system with a blue supergiant star. The black hole is about 7,000 light years away and was the first that was generally accepted to be a black hole.

4. Gaia BH1

   Gaia BH1 is a 9-solar-mass stellar black hole in a binary system with a Sun-like star. At only 1560 light years away, it’s currently the closest known black hole to Earth.

5. TON 618

   TON 618 is a very massive supermassive black hole, with a mass of about 40 billion solar masses. It’s approximately 18 billion light years away from Earth.

6. Phoenix A*

   Phoenix A is a very massive supermassive black hole, with an uncertain mass estimated to be on the orders of billions of times the mass of our Sun. Some estimates even put it at 100 billion solar masses, which would make it the most massive known black hole to date.

7. M31*

   M31* is a supermassive black hole in the center of the Andromeda galaxy. Its mass is estimated to be about 200 million solar masses. Although it’s a common misconception that black holes are the densest objects in the universe, this only applies for the stellar-mass kind: M31* is only approximately as dense as water!

8. RX J1131-1231

   RX J1131-1231 is a supermassive black hole located 6 billion light years from Earth. In 2014, astronomers discovered that x-rays were being emitted from very close to the black hole, which would only be possible if the black hole was spinning very fast: at least half the speed of light! RX J1131-1231 was the first black hole to have its rotation directly measured in this way, although it’s believed that all black holes are spinning.

9. Great Annihilator

   The Great Annihilator is a stellar-mass black hole. It routinely emits massive amounts of photon pairs, which suggests the annihilation of a large number of electron-positron pairs: Hence the name, the Great Annihilator.

10. The Unicorn

    The Unicorn is a very small black hole located only about 1500 light years from Earth. It is barely 3 solar masses, making it one of the least massive known black holes.

The Contenders

11. Holmberg 15A