What is the maximum mass limit for a stable white dwarf star?

The maximum mass limit for a stable white dwarf star is the Chandrasekhar limit. For a typical non-rotating white dwarf made largely of carbon and oxygen, it is about 1.4 times the mass of the Sun, commonly quoted as approximately 1.44 solar masses.

A white dwarf is supported against gravity by electron degeneracy pressure, a quantum-mechanical effect arising from the Pauli exclusion principle. As the star gains mass, its electrons are forced into increasingly energetic states. At extreme density, the electrons become relativistic, and the pressure no longer rises sufficiently to support additional mass. The star then approaches the limiting mass calculated by Subrahmanyan Chandrasekhar.

Chandrasekhar developed the decisive relativistic model in 1930–1931. His work initially faced strong criticism from Arthur Eddington, but the limit became fundamental to theories of stellar evolution. A white dwarf nearing the limit may ignite runaway carbon fusion and produce a Type Ia supernova; an oxygen–neon–magnesium white dwarf may instead collapse into a neutron star.

The value is not absolutely identical for every case. Composition, temperature, magnetic fields, and rotation can alter the idealized limit, but the Chandrasekhar limit remains the canonical answer.