About Black holes...

Black Holes are some fascinating objects found in space. Having such an extreme density as well as strong gravity even light cannot escape from their grasp. The term Black Hole was first coined by John Wheeler in 1967 though it was first predicted by Albert Einstein in 1916 with his GTR.
Generally three types of Black Holes are found- Stellar black holes, supermassive black holes and intermediate black holes.

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Smaller Stars which are about three times the sun’s mass when burnt through the last of its fuel form a neutron star or white dwarf. But when a larger star collapses it continues to squeeze and forms a stellar black hole. Black holes which are formed by individual stars are heavily densed. It consumes a great amount of gravitational energy to pull objects around it. According to a report MILKY WAY contains a few hundred million stellar black holes.
Supermassive black holes are billions of times as massive as sun. Such black holes are supposed to lie at the center of every galaxy. Once they formed, they gather masses from the surrounding dust and gas around them , the materials around the center of galaxies allow them to grow bigger sizes. They might be the results of thousands of tiny black holes merged together.
The third one is the intermediate black hole. Scientists revealed that it could be formed when stars in a cluster collide in a chain reaction. Several these type of forming fall together in the center of the Galaxy to create a supermassive black hole.

As scientists cannot see the Black holes, they must rely on the radiation that is emitted as dust and gas are drawn in the densed creature. Supermassive black holes , as are shrouded by dust and gas thick around them which can block the telltale emission. The event horizon of a black hole is the boundary around the black hole where the light losses its ability to escape. As the gravity is constant across the event horizon ,once a particle crosses it cannot leave .The mass of the black hole is concentrated at a point which is called singularity. It is a point of zero volume and infinite density. It sounds impossible!!!
Theories of quantum mechanics are employed to tackle this problem how gravity behaves on the smallest possible strengths and densities of matter. There are a numbers of approaches been taken including thelatest string theory but till now there is not any strong front runner.