Neutron stars and black holes

Like white dwarfs, neutron stars are strongly degenerate compact objects of roughly one solar mass. But whereas white dwarfs are supported against gravity by the zero-point motion of electrons (electron degeneracy pressure), neutron stars, as the name suggests, consist mostly of neutrons and are supported by the zero-point motion and interactions among the latter particles. The existence of neutron stars was hypothesized by Lev Landau and by Walter Baade and Fritz Zwicky shortly after the discovery of the neutron by Chadwick in 1932—Baade and Zwicky even proposed that neutron stars might form in supernovae, as is now believed. However, the observational history of neutron stars began only in 1967 with the discovery of radio pulsars by Jocelyn Bell and her Ph.D. advisor A. Hewish. In the meantime, the properties of such stars had been elucidated by a few important theorists, including J. R. Oppenheimer and E. Salpeter. For more historical and physical detail than can be fit into this lecture, see the book by Shapiro and Teukolsky. We have seen that white dwarfs have a maximum mass