Existence of Black Hole was predicted by Albert Einstein in 1916 in General Theory Of Relativity.
American Scientist John Archibald Wheeler coined term Black Hole many year later in 1967.
"The body is "Black Hole" if it's all mass is inside a sphere with Schwarzchild radius. "
Schwarzchild radius =2GM/c²
Where M is mass of body, G is gravitational constant and c represent the speed of light.
*The boundary of a Black Hole is called its event horizon.
*The escape speed from a Black Hole is equal to the speed of light c at the Schwarzchild radius, hence nothing at all can leave the black hole.
*For a star with Sun's mass, Schwarzchild radius is 3Km, a quarter of a million times smaller than Sun's present mass.
* Black hole is the region of strongest gravitational field in space.
Singularity :
The center of Black Hole where object's mass lies is known as singularity, the single point in space-time where the mass of Black Hole is concentrated.
American Physicist Kip Thorne describes it as " the point where all the laws of physics break down."
Formation Of Black Hole:
A Black Hole is formed by the death of a massive star,when such star has exhausted the internal thermonuclear fuel in its core at end of its life. The core becomes unstable and gravitationaly collapses inward upon itself.
Types Of Black Hole:
* Stellar Black Hole:
Mass of Stellar Black Hole is between 10 to 100 times of solar masses.
*Intermediate Black Hole:
If the mass of Black Hole is between 100 to 100000 times of solar masses then it is called intermediate Black Hole.
*Supermassive Black Hole:
A Supermassive Black Hole is the largest type of Black Hole with mass on the order of millions to billions of times the mass of sun. Almost every large galaxy has Supermassive Black hole at its center.
The supermassive Black Hole that lurks at the center of our galaxy is called Sagittarius A*.
*Miniature Black Hole:
This type of Black Hole exist only in theory so far. These can be wide as atomic particle but have mass of Mount Everest. They may have formed soon after the Big Bang.
Detection Of Black Hole:
A Black hole that is member of a double star system will reveal its presence by its "gravitational pull on the other stars" , the two stars circle each other. The intense gravitational field of Black Hole will attract matter from other star which will be compressed and heated to such a high temperature that x-ray emitted profusely.
Closest Black Hole To The Earth :
The closest Black Hole to the Earth is Saggittarius A* that lies 26,000 light years away from us. There are no Black Holes close enough to Earth to effect us if Earth gets within about 800,000Km of this Black Hole it will get pulled apart.