Chandrasekhar Limit

The Chandrasekhar limit is the maximum mass that a white dwarf star can support against gravitational collapse through electron degeneracy pressure alone. It is approximately 1.4 solar masses. Above this limit, electron degeneracy pressure is insufficient to resist gravity, and the star must either collapse into a neutron star or explode as a Type Ia supernova.

The limit was derived by Subrahmanyan Chandrasekhar in 1930 using a combination of quantum mechanics and general relativity. It represents a fundamental boundary in stellar astrophysics, separating the fate of low-mass stars from high-mass stars. The Chandrasekhar limit is also the reason Type Ia supernovae are standardized: every white dwarf that approaches this mass explodes at the same peak luminosity, making them reliable standard candles for measuring cosmic distances.

The Chandrasekhar limit is often presented as a number — 1.4 solar masses — but it is more than that. It is a phase boundary in the equation of state of matter, a point where the quantum mechanical behavior of electrons meets the geometric curvature of spacetime. The limit is not arbitrary. It is where two fundamental theories cross, and the crossing produces a catastrophe.