Pulsars and Isolated Neutron Stars

The idea of neutron stars can be traced back to the early 1930s, when Subrahmanyan Chandrasekhar discovered that there is no way for a collapsed stellar core with a mass more than 1.4 times the solar mass, M{in⊙}, to hold itself up against gravity once its nuclear fuel is exhausted. This implies that a star left with M > 1.4 M{in⊙} (the Chandrasekhar limit) would keep collapsing and eventually disappear from view.