HISTORY – THEORY LEADS, FOR ONCE

In 1932, the brilliant Russian physicist Lev Landau argued on general grounds that the newly discovered quantum pressure could not support a mass much in excess of 1 solar mass. He addressed his discussion to electrons, but the type of particle did not matter. In 1933, the neutron was discovered, after Landau's paper had been submitted. In retrospect, Landau's arguments applied to the quantum pressure of neutrons as well. An object supported by the quantum pressure of neutrons should be smaller and denser than a white dwarf, but it should have nearly the same maximum mass, about 1 solar mass.

Fritz Zwicky of Caltech was one of the world's first active supernova observers. Quick on the pickup, Zwicky suggested in 1934 that supernovae result from the energy liberated in forming a neutron star. Not until a year later, in 1935, did the precocious young Indian physicist, Subramanyan Chandrasekhar, present his rigorous derivation of the nature of the quantum pressure and the mass limit to white dwarfs that bears his name.

Robert Oppenheimer made history with his leadership of the Manhattan Project, but among his most widely known papers are two published with students in 1939. The first of these papers used the complete theory of general relativity for the first time to estimate the upper mass limit of neutron stars to be 0.7 solar mass. The second paper explored the result of violating that limit with the resulting production of a black hole.