The Chandrasekhar Mass

Indian theoretical astrophysicist Subrahmanyan Chandrasekhar predicted while a very young man in the 1930s that there was a limiting mass for white dwarf stars. No white dwarf could be stable against gravitational collapse if it exceeded this mass, which is about 1.4-1.5 solar masses, depending on the detailed composition of the white dwarf.

Shrinking Radii

The result of this theory is illustrated in the adjacent figure. As mass is added to the white dwarf it shrinks, contrary to intuition. The limiting mass is defined as the point where the radius would shrink to zero. No white dwarf can exist at that mass or beyond. (Later we will ask what happens to a white dwarf that tries to form with more than the limiting mass. The answer to that question will be very interesting indeed.)

Degeneracy versus Gravity

At the heart of Chadrasekhar's theory is the issue of how a degenerate gas of electrons behaves if the white dwarf is made more and more massive. The solution of the problem required the application of both the newly invented theory of quantum mechanics and of relativity. In essence, Chandrasekhar's theory showed that even electron degeneracy pressure was not sufficient to win the battle against the relentless pull of gravity once the mass exceeded a critical value.