History of the term Black hole is quite interesting. In 1687 Sir Isaac Newton first described the term gravity in his publication “Principia”. We all know that gravity of black hole gives nightmare to scientists. In 1783 John Michell predicted that there might exist an object whose escape velocity is more than the speed of light. Albert Einstein predicted the space-time curvature in his theory of Relativity in 1915. In 1916 Karl Schwarzschild's using Einstein’s theory of relativity explained Blackhole and also defined the gravitational radius of a black hole, which afterward called as Schwarzchild radius. After that, black hole theory was strongly opposed unless John Wheeler came in and coined the term Black hole again. In 1964 neutron stars were discovered and in 1970 Stephen Hawking described the black hole briefly. In 1994 Hubble telescope provided the best evidence of supermassive black holes.
Black holes are the most interesting objects in the universe. A black hole is, in fact, a large amount of matter packed into a small area. Nothing can escape from the black hole, not even light. The formation of a black hole is quite interesting phenomena. The formation of the black hole takes place when any object reaches a critical amount of density and its gravity causes to collapse to a small point. There are two types of black holes, stellar black holes, and supermassive black holes. Stellar black holes are mostly formed when a star less 100 times to that of the sun’s mass collapses. In reality, an end of a star is a beginning of a black hole. If a star is massive as three times the mass of the sun than theoretically it can be proved that no force can save a star from collapsing under its own gravity. In the case of our sun, the chances of forming a black hole are none because our sun’s mass does not fulfill the criteria. Stellar black holes are formed by an explosion. When a star runs out of fuel then it collapses and forms a supernova and remaining matter forms a black hole.
In the case of Super Massive Hole we are not quite sure what causes the formation of a super massive black hole, but it is pretty sure that super massive black holes are more massive than a stellar black hole. Some say that a group of stellar black hole together after merging makes super massive black holes. One possibility is that in early ages of the universe some stellar black holes are formed and with time they are transformed to a super massive black hole.
Scientists think that there is no middle category of a black hole, but recent indications from Chandra, XMM-Newton and Hubble are giving strength to a middle category of Black holes. Around 20 X-ray binary systems that are thought to contain stellar black holes have been discovered and this number continues to increase the sensitivity of tool advances. The Large Hadron Collider in Switzerland that may reach energies high enough to create tiny black holes.