What is Black Hole

                                     The Black Hole

Black Hole itself is a name that has absorbed a lot of mystery in it, so today we will discuss about Black Hole.

The man who had first published his views about the black hole in front of the world, was Professor John Michell (1724-1793), who was a professor at University of Cambridge had given his thoughts about black holes in 1783. After him in 1796, a scientist from France Pierre Simon (1749-1827) has explained the black hole in his book "The system of the world".

Black hole is that body in the Universe whose gravitational power is so much that even light can not be passed across it and if any thing coming near it, black holes swallows that thing. Not only this, the closer the thing passes to the black hole, the effect of  time also diminishes and there is no existence of time within the black hole circle.

                                                      How Black hole was made  

Black holes are an extremely dense object. In the universe, if we shorten any object by compressing it, then it mass and density will increase its gravitational force so much that even light cannot passed through it and that thing is called black hole. If the density of our earth increases too much and by simply compressing the whole earth to 1.5 cm, its gravity will increase and it will also become a black hole.

 Similarly if we shorten sun by compressing it, it will also become a black hole, but remember that the density is very important in comparison to the mass in the black hole, and the earth and the Sun are not shrinking in this way, because neither the earth nor the gravitational forces of the sun are so

strong.

But if a star hundreds of times bigger than our Sun, whose mass and density are very high, become a black hole with these properties, and most of the black holes are made of such stars.

The Stars are born by the clouds of galvanized dust and gas particles present in the galaxy and these clouds made of gas are called Nebula (A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases) and when percentage of density increases in the Nebula, then this cloud starts to be compressed automatically and the heat inside it so high that the molecules of hydrogen and helium collide with each other and make a round shape and in this way stars created.

But in the process, many millions of years have passed. Our Sun was also created like this and when the hydrogen dies in the stars, the star starts to cool down slowly.

Now, the stars that have ended their own fuel, can not keep themselves stable against their own gravity, and an explosion inside such stars occurred , which is called Supernova.

"A supernova is a transient astronomical event that occurs during the last stellar evolutionary stages of a massive star's life, whose destruction is marked by a final titanic explosion. This causes the sudden appearance of a "new" bright star, before slowly fading from sight over several weeks or months".

After this explosion, if any part of that star remains which is very dense, then it becomes a highly dense Neutron star. Due to the immense gravity pull on such stars, the star starts to be compressed and compresses up to a limit and becomes a black hole.

The entire mass of a black hole is centered in a small point called the Central Singularity Point. The circular boundaries around this point are called Event Horizons. Any object falling in the black hole divides into molecules and due to its high density, they move to a place which has not been found yet.

                                                  Types of Black Hole 

There are many types of black holes in the universe:

Such stars whose mass is few times greater than our sun, and become black hole due to shrinkage, it is called Stellar Mass Black Holes.

The black hole that is built in the centre of the galaxy and whose density is immense and which are very vast are called Super Massive Black Holes. Mass of  such black holes have millions of times more than our sun. There is a Super massive black hole in the middle of our Milky Way Galaxy, which is 10 million times more than our Sun.

There are also black holes in which the mass is less than our Sun, it is called Primordial or Small black hole. According to Stephen Hawking, we can learn about the origin of the universe by studying such a black hole.

Black holes are actually no holes, they are mere remains of a dead star. After passing crores of years, a star is ending and is born as a black hole.
All stars do not become black holes. Some black holes can also pull the entire Galaxy up towards him. Black hole does not pull the object outside its gravitational force. About Black hole, it was said from the time of Michell but the first black hole coming in front of the world was Cygnus X 1 and it was confirmed in 1972.