But if the star is really massive, it will explode as a supernova and go on contracting into a point of infinite density where matter is compressed beyond our understanding and form a black hole. In Quantum Physics, there is a law known as the Exclusion Principle, which states that no two particles can have the same quantum state, that is, the same spin and sub-level of energy in the orbital model. As the dying star collapses onto itself and gravity becomes increasingly high, putting particles together, these have to move at greater velocities in order to not have the same state. But there is a physical limit to the velocities that particles can attain, which is the speed off light, unsurpassed by anything in our Universe. So when the particles get so close together that in order not to share the same quantum numbers they would have to move at speeds faster than light the exclusion principle is no longer valid.
Gravitational attraction claims victory and there is no end to the contraction.
The star will inexorably become a singularity of infinite density, a black hole. Although a black hole's density is infinite, for it occupies a point in space, its mass is the finite value that corresponds to the mass of the star that originated it and gravity still can be calculated according to Newton's law of universal gravitation. The common misconception is that black hole has infinite gravity and that it will swallow everything. If that were so and the gravity of a black hole was truly infinite, then all celestial objects, regardless of the distance to them would be in jeopardy of being absorbed by it. Fortunately, the black hole initially has the mass of its originating star and consequently its same gravitational attraction.