Introduction to Black Hole 

The Black Hole

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

 It is also a region that has a very strong gravitational effect that nothing can escape from it, including light. The smallest black hole is XTE J1650-500. The black holes are extreme places. They swallow almost everything that comes into it . This does not  mean that the black holes also must always be the same huge. In fact, there are miniature versions such as XTE J1650-500, an object that is located at a distance of 10,000 light years to Earth. With a weight of only 3.8 solar masses and a diameter of just 24 kilometres, it is one of the smallest black holes.

Because no light can get out, people cannot see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

The theory of general relativity predicts that a sufficiently  mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon.  In many ways a black hole acts like a black body, as it reflects no light whatsoever. 

Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace.

Around a black hole there is a position of no return, called the event horizon. It is called "black" because it absorbs all the light that hits it, reflecting nothing, just like a perfect black body in thermodynamics. 

A black hole is found by its interaction with matter. A black hole can be inferred by tracking the movement of a group of stars that orbit a region in space. Alternatively, when gas falls into a black hole caused by a companion star or nebula, the gas spirals inward, heating to very high temperatures and emitting large amounts of radiation. This radiation can be detected from earthbound and Earth-orbiting telescopes.

Bibliography-1).http://www.werebel.net/the-most-extreme-places-in-the-universe-to-live/
                       2).Google Images.
                       3).http://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-     black-hole-k4.html
                       4).https://en.wikipedia.org/wiki/Black_hole
                       5).https://simple.wikipedia.org/wiki/Black_hole