What is the Chandrasekhar limit?

The Chandrasekhar limit (~1.44 M☉) is the maximum mass a white dwarf can support through electron degeneracy pressure. Above this mass the pressure cannot counteract gravity, causing the star to collapse or explode.

What is mu_e (mean molecular weight per electron)?

mu_e is the average mass (in atomic mass units) per free electron in the stellar material. For fully ionized carbon or oxygen, mu_e ≈ 2. For helium, mu_e ≈ 2. For iron, mu_e ≈ 2.15. A higher mu_e means fewer electrons per unit mass, reducing degeneracy pressure and lowering the mass limit.

What happens when a white dwarf exceeds the Chandrasekhar limit?

One of two outcomes occurs: (1) A Type Ia supernova — for typical carbon-oxygen white dwarfs where carbon fusion ignites explosively, destroying the star entirely. (2) Collapse to a neutron star — if electron capture reactions proceed before ignition. Both events are catastrophic and release enormous energy.

Why are Type Ia supernovae called standard candles?

Because they always explode near the same mass (the Chandrasekhar limit), they release nearly the same total energy. This makes their intrinsic brightness predictable, so astronomers can use their observed brightness to measure cosmic distances — a method that led to the discovery of dark energy.

Is the 1.44 M☉ value exact?

No — it is an approximation from the simplified formula. The full numerical calculation gives ~1.4 M☉ for mu_e = 2. Factors such as rotation, magnetic fields, and general relativistic corrections can shift the true limit slightly. Super-Chandrasekhar white dwarfs (up to ~2 M☉) have been observed, likely supported by rapid rotation.

What is the formula used?

The standard approximation is M_Ch = (5.87 / mu_e²) M☉, derived by Chandrasekhar in 1931 from relativistic quantum mechanics. The constant 5.87 encodes the Planck constant, speed of light, gravitational constant, and proton mass.

Chandrasekhar Mass Calculator

Name: Chandrasekhar Mass Calculator
Availability: InStock
Author: Nham Vu

Enter the mean molecular weight per electron to compute the Chandrasekhar limit — the maximum mass a white dwarf can hold before collapsing.

White Dwarf Parameters

Mean Molecular Weight per Electron (mu_e)

Carbon/oxygen: 2.0 | Helium: 2.0 | Iron: ~2.15

Preset Compositions

Formula

M_Ch = 5.87 / mu_e² × M_☉

Derived from relativistic electron degeneracy pressure (Chandrasekhar, 1931). The constant 5.87 encodes G, c, h, and m_p.

Enter mu_e and click Calculate

Results will show the Chandrasekhar limit in solar masses, kilograms, and Earth masses.

Summary

Enter the mean molecular weight per electron to compute the Chandrasekhar limit — the maximum mass a white dwarf can hold before collapsing.

How it works

Enter the mean molecular weight per electron (mu_e) — use 2 for carbon/oxygen, 2.15 for iron.
The calculator applies M_Ch = (5.87 / mu_e²) solar masses.
Results appear in solar masses, kilograms, and Earth masses.
The fate panel shows what happens if the limit is exceeded based on the white dwarf composition.
Use the preset composition buttons to quickly explore common white dwarf types.

Use cases

Astrophysics students studying stellar evolution and degenerate matter.
Understanding why Type Ia supernovae are standard candles in cosmology.
Exploring how white dwarf composition affects the mass limit.
Comparing the Chandrasekhar limit to neutron star mass limits.
Science writing and science fiction world-building with accurate stellar physics.
Verifying textbook formula results with an interactive calculator.

Frequently Asked Questions

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Last updated: 2026-05-29 · Reviewed by Nham Vu