Black hole is an empty place in space where the gravitational pulls are so heavy that even light cannot escape it. When a star dies, the matter around it squeezes into a singular space after a supernova. This space has a strong gravity and pulls anything into it.
No light can get out of a black hole and hence anyone trying to see a black hole on a telescope will only be able to view a disc of light that emits as a result of pulling of a star. Otherwise, the black hole is entirely invisible unless some special tools are used.
Albert Einstein was the first to predict about black holes in 1916, and since then produced the theory of relativity around it. In late 1967, American astronomer John Wheeler coined the term black hole. Until now, three types of black holes have been classified.
Stellar black holes are formed by the collapse stars that are incredibly small and dense. They pack more matter when they form and as a result will have the strongest gravitational pull. The other is the intermediate black hole that forms when a star cluster collides in a chain reaction. Several black holes take into formation and fall together as one. Another is the supermassive black hole that forms when hundreds or thousands of tiny black holes get together.
The first black hole to be discovered is the Cygnus X-1. In 1971, rockets that were carrying Geiger counter detected radio emissions coming from a compressed place in space. Some new X-ray sources were found and were detected to be coming from the black hole.
Anything that passes closer to the black hole will fall into it and get torn apart. Astronomers also estimated that there will be around a billion of stellar black holes in the Milky Way and many are yet to be identified. Since black holes don't move around, the possibility of Earth falling into a black hole is very rare and the sun is also not a big star to turn into a black hole.
Watch the video about black holes below: