Neutron star

       A supernovae occurs when a giant star collapses to the density of an atomic nucleus. At such a tremendous high densities, protons and electrons are fused together into neutrons. The neutrinos that are made in the iron core as protons are converted to neutrons.
          So after the explosion, the outer layers gets blow off in an often-spectacular display, leaving behind a sphere of tightly packed neutrons, a neutron star. It may roughly contain 10^57 neutrons with the mass between 1 and 3 solar masses.
        When the core of pre-supernovae star collapses into a neutron star, it's temperature can go up to trillions of degrees. At that particular point, star gives off gamma rays. Then it stars shrinking and cools. Initially the cooling is fast but as time passes it Starts cooling slowly. Because it has so little surface fir heat to radiate , it may have several thousands if degrees.
          Neutron stars even produce a significant amount of blackbody radiation. The gravitation acceleration for a neutron star is 100 billion times than that of earths gravitational acceleration. The escape velocity of a neutron star is about half the speed of light. Neutron stars can spin as fast as 43,000 times per minute, but gradually slows over time. And neutron stars contain the strongest magnetic fields known in the universe.
        The outer layers of the neutron star are under less pressure and there the neutrons are less stable and tend to decay into normal matter. But throughout the star, there is a balance, between neutrons and other material, with neutrons becoming protons and electrons and then protons and electrons becoming neutrons again.
         The neutrons themselves have intrinsic magnetic moments (since they are made of quarks) and the incredibly high energies inside the neutron star can, not only create particle/antiparticle pairs, but can also create exotic particles as well.