Neutron Star

A neutron star is a type of stellar remnant that can result from the gravitational collapse of massive star during a Supernova event.

Neutron star is the last phase of star's life in which mass of inert core after nuclear fusion reaction is greater than the Chandrasekhar limit of White Dwarf, but its mass is not great enough to overcome neutron degeneracy pressure to become Black Hole.

Formation

Any star with a initial main sequence mass of around 10 solar masses or above has the potential to become a neutron star. As the star evolves away from the main sequence, subsequent nuclear reaction produces an iron rich core. When all nuclear fuel in the core has been exhausted, the core must be supported by degeneracy pressure alone.