Chandrasekhar Limit — White Dwarf Mass Calculator
Calculate the Chandrasekhar mass limit for white dwarfs using electron degeneracy pressure.
Understand why this limit triggers Type Ia supernovae.
The Chandrasekhar limit is the maximum mass a white dwarf star can have before electron degeneracy pressure can no longer support it against gravitational collapse.
Formula (Chandrasekhar/Kapustinskii approximation):
M_Ch ≈ 5.87 / μ_e² × (ħc/G)^(3/2) / m_H²
This simplifies to:
M_Ch ≈ 1.44 / μ_e² × M☉
Where μ_e is the mean molecular weight per electron:
- μ_e = 2 for carbon-oxygen white dwarfs (one electron per two nucleons): M_Ch ≈ 1.44 M☉
- μ_e = 1 for pure hydrogen: M_Ch ≈ 5.76 M☉ (theoretical — such stars don’t exist as white dwarfs)
- μ_e ≈ 2.15 for oxygen-neon cores: slightly lower limit
The limit was calculated by Subrahmanyan Chandrasekhar in 1930 while sailing to England at age 19. He was awarded the Nobel Prize in Physics in 1983.
Physical interpretation: When a white dwarf exceeds 1.4 M☉ (typically via mass transfer from a binary companion), electron degeneracy pressure fails. The star can no longer support itself. The entire star ignites in a thermonuclear explosion: a Type Ia supernova.
Type Ia supernovae as standard candles: Because the Chandrasekhar limit is nearly the same for all white dwarfs, Type Ia supernovae reach nearly identical peak luminosities. This makes them extremely valuable as standard candles for measuring cosmic distances — they were used to discover the accelerating expansion of the universe in 1998.
Real white dwarfs: Observed white dwarfs have masses ranging from about 0.5 M☉ to just below 1.4 M☉. The most massive known white dwarf is RE J0317-853, close to the Chandrasekhar limit.