THE BLACK HOLE BESTIARY
As with many other celestial bodies, black holes can be split into classes
1 Miniature black holes
Still hypothetical, these black holes have a mass smaller than the Sun. They were first proposed by Stephen Hawking in 1971, who suggested they may have formed in the early Universe. Some experts claimed miniature black holes might appear in the collisions created by the Large Hadron Collider, but none have been detected so far.
3 Intermediate mass black holes
Ranging from 100 to 100,000 solar masses, only a handful of these black holes have been discovered. They have been proposed as the seeds of supermassive black holes. A Japanese team recently announced finding one close to the Milky Way’s own supermassive black hole, adding fuel to the idea that these titans are formed by the merger of their smaller cousins.
2 Stellar-mass black holes
These black holes, between about 4 and 100 solar masses, are thought to be the most abundant of the four classes. Formed from the core-collapse of massive stars at the end of their lives, the nearest known one is V616 Monocerotis. It is located about 3,000 lightyears away, and is between 9-13 times the mass of the Sun.
4 Supermassive black holes
These can be anywhere from between 100,000 and 50 billion times the mass of the Sun. They exist at the heart of most large galaxies; even the Milky Way has one, Sgr A*. Its 1974 discoverers, Bruce Balick and Robert Brown, added an asterisk to signify the discovery was ‘exciting’. Sgr A* is 4.1 million times more massive than the Sun.