What is a black hole?
A black hole is a region of space containing matter so dense light is unable to travel through it fast enough. The gravitational pull is so great light is unable to escape, making black holes invisible to the naked eye.
How are they detected?
Black holes are detected by their effect on surrounding galaxies, stars and dust. For example, if a star is near to a black hole, high-energy light is made, which can then be picked up by satellites and telescopes.
Black holes are found within quasars; distant celestial bodies.
How are they formed?
Scientists have three theories.
1) They believe the smallest black holes formed at the conception of the universe.
2) When the centre of a particularly big star collapses, stellar black holes are created. This causes a supernova, which is when an exploding star blasts parts of itself into space.
3) The largest black holes are called supermassive black holes. They were, scientists believe, formed at the same time as the galaxy they are in.