How is a black hole created?

There is an attractive force of gravitation that acts
between all bodies with mass. Under normal circumstances there are several repulsive
forces which include those between sub-atomic particles that exceed the attractive force
of gravity.

In the case of stars, the gravitational force
of attraction between the atoms of gas that makes up the stars is initially less than
the repulsion due to energy released by fusion. When stars have used up all their fuel
and no more energy is being released due to fusion different phenomena take place
depending on the initial mass of the star. The lighter ones explode to form what is
called a supernova, most of the mass is expelled and a small amount of mass called a
white dwarf is left behind.

If the mass of the star is more
than 3-4 times that of the Sun, after fusion stops, there is enough mass to start a
collapse of the star inwards and there is no opposing force; even that of the force of
repulsion between sub-atomic particles does not exceed the attractive force of gravity.
As the star collapses, its gravitational force increases and so does the rate of
collapse. The result of this gravitational collapse finally creates a body with an
infinitely powerful gravitational field from which nothing can escape. This is a Black
Hole.