The final evolutionary stage for larger stars, in which they have exhausted their thermonuclear fuel and radiate relic heat. Neutron stars are extremely dense and are supported by neutron degeneracy pressure.
A neutron star is the remnants of a dead supergiant. When the star collapses, the negatively charged electrons are combined with the positively charged protons, which forms neutral neutrons. Thus the name, neutron star. This small dense ball of matter, contains all the mass and magnetic field of the star's core.
Stars born with about 8 to 20 times the mass of the Sun blast most of their material into interstellar space in titanic explosions, leaving only their crushed, dense cores, called neutron stars. Neutron stars are named after their composition: neutrons. In a star with a core that is 1.4 to 3 times the mass of the Sun, the core collapses so completely that electrons and protons combine to form neutrons. A full bathtub of neutron-star material (instead of water) would weigh as much as two Mount Everests. A neutron star is about 10-15 miles (16-24 km) in diameter, with a liquid neutron core and a crust of solid iron. Some neutron stars, called pulsars, spin rapidly (from once a second to several hundred times per second) and generate powerful magnetic fields.