Neutron Stars and Black Holes

If the remnant core left after a supernova has a mass greater than the Chandrasekhar limit (1.44 M_☉, where M_☉ is one solar mass), electron degeneracy pressure cannot support it, and gravity continues the collapse.The electrons are forced to combine with protons to form neutrons (releasing neutrinos). The result is a neutron star: a core made almost entirely of neutrons. A neutron star is incredibly dense, similar to the density of an atomic nucleus (of order 10¹⁷ kg m⁻³). A mass of one or two solar masses is packed into a sphere only about 20 km across. It is supported against further collapse by neutron degeneracy pressure. Many neutron stars spin rapidly and are observed as pulsars.If the remnant core has a mass greater than about 3 M_☉, even neutron degeneracy pressure cannot stop the collapse, and the core collapses to a black hole.A black hole is an object whose gravitational field is so strong that the escape velocity from it is greater than the speed of light, c. Nothing, not even light, can escape from inside a boundary called the event horizon. The core is thought to collapse to a point of infinite density called a singularity.Summary of the fate of a remnant core of mass M:M < 1.44 M_☉ → white dwarf
1.44 M_☉ < M < 3 M_☉ → neutron star
M > 3 M_☉ → black hole