A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich.[1] Except for black holes and some hypothetical objects (e.g. white holes and quark stars), neutron stars are the smallest and densest currently known class of stellar objects.[2] Neutron stars have a radius on the order of 10 kilometres (6 mi) and a mass of about 1.4 solar masses.[3] They result from the supernova explo