ExploraTour: A Peek into the Lives of the Stars
How Can Such High Densities Exist?
An atom contains mostly empty space -- the nucleus and electrons are really very small compared to the volume the atom occupies. In a neutron star, all of the electrons and protons have been squeezed together to form neutrons and nearly all of the space in the atom has been removed.
Quantum theory predicts that no two neutrons occupying the same region in space, can be in the same state. As the neutrons are squeezed together all of the lower energy states are filled and neutrons that are added to the region must be added in higher and higher energy states.
Intense pressure can be generated in the degenerate neutron gas sufficient to halt the gravitational collapse. Since neutrons are 2000 times heavier than electrons, the pressure generated by the degenerate neutrons is much greater than that generated in white dwarfs by degenerate electrons.