what is a black hole?

we have all heard about black hole in our life. its very mysterious and make us wonder what is it, how does it exist, what it can do. today i will try to explain it.

Normally, when a star is alive, the inward for of gravity is exactly balanced at each point by the outward force created by hot gases and radiation.
these inward and outward forces maintance balance and hold the star together.

however, when the star runs out of fuel, there are no hot gases and radiations.

hence, there is no outward force to balance the inward pull of the gravity and thus, star begins to die.
the star's cores began to collapse under its own gravity.
this collapse causes the outer layers to blow apart in a huge explosion called a supernova.

now, it is estimated that if a star has atleast 20 times of mass than our sun then star collapses to form a black hole.

the surface and the boundary of a black hole is called event horizon.
nothing can escape from event horizon of a black hole, not even light.
hence, the black hole appears black.