Low or medium-mass stars are not heavy enough to become neutron stars. While a star is 'alive' there are two forces acting on it: Gravity crushes the star inward while outward pressure (caused by the heat that the star generates) tries to make the star explode outward. As long as the star has fuel to burn, these two forces remain balanced.
When a massive star runs out of nuclear fuel, it can no longer geneate enough heat to resist gravity and it starts to collapse in on itself. Eventually, as the star collapses, the electrons are forced into the protons (converting them to neutrons) and quantum effects prevent the star from collapsing any further. This is called a neutron star. If the star is even more massive, then it can overcome this quantum effect and produce a black hole.
Small or medium mass stars never reach this point. That's because, as they collapse, the electron shells of the individual atoms composing the star prevent it from ever compressing enough to form a neutron star or black hole. A star like this is called a white dwarf.
When a massive star runs out of nuclear fuel, it can no longer geneate enough heat to resist gravity and it starts to collapse in on itself. Eventually, as the star collapses, the electrons are forced into the protons (converting them to neutrons) and quantum effects prevent the star from collapsing any further. This is called a neutron star. If the star is even more massive, then it can overcome this quantum effect and produce a black hole.
Small or medium mass stars never reach this point. That's because, as they collapse, the electron shells of the individual atoms composing the star prevent it from ever compressing enough to form a neutron star or black hole. A star like this is called a white dwarf.