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⚪ Chandrasekhar Limit Simulator — White Dwarf Collapse

Interactive Chandrasekhar limit simulation. Add mass to a white dwarf star via accretion and watch electron degeneracy pressure hold it stable — until it crosses roughly 1.4 solar masses and collapses into a supernova or neutron star.

Space & Astronomy3DModerate60 FPS

This interactive simulation lets you pile mass onto a white dwarf star through simulated accretion from a companion star and watch what happens as it approaches, then crosses, the Chandrasekhar limit — the roughly 1.4 solar mass ceiling beyond which electron degeneracy pressure can no longer hold the star up against gravity.

🔬 What It Demonstrates

A white dwarf is supported by electron degeneracy pressure, a quantum-mechanical effect (from the Pauli exclusion principle) rather than thermal pressure. As mass increases, the star actually shrinks (radius roughly falls as M^-1/3), squeezing electrons to relativistic speeds. Subrahmanyan Chandrasekhar showed in 1930 that above about 1.4 solar masses, relativistic degeneracy pressure can no longer win, and the star must collapse.

🎮 How to Use

Drag the mass slider up, or use Add mass and Start continuous accretion to simulate matter flowing from a companion star. Toggle composition between carbon-oxygen and oxygen-neon to see the slightly different limiting mass and outcome, and adjust surface temperature to change the star's colour. Once the limit is crossed, watch the collapse sequence play out, then press Reset to try again.

💡 Did You Know?

A carbon-oxygen white dwarf that reaches the limit typically detonates entirely as a Type Ia supernova via runaway carbon fusion, leaving no compact remnant — and because these explosions reach a strikingly consistent peak brightness, they are used as "standard candles" to measure cosmic distances. An oxygen-neon white dwarf, however, can instead undergo electron-capture-induced collapse directly into a neutron star.

About this simulation

The Chandrasekhar limit, named after astrophysicist Subrahmanyan Chandrasekhar who derived it in 1930, is the maximum mass — about 1.4 solar masses for a typical carbon-oxygen composition — that a white dwarf star can have while still being supported by electron degeneracy pressure. This simulation models a white dwarf gaining mass through accretion from a companion star in a binary system, shrinking as predicted by the mass-radius relation for degenerate matter, until it reaches the limit and one of two dramatic fates unfolds depending on its internal composition.

🔬 What it shows

A simplified mass-radius relation in which the white dwarf's radius shrinks as its mass grows and drops toward zero as the mass approaches the Chandrasekhar limit, reflecting how relativistic electron degeneracy pressure weakens relative to gravity. Crossing the limit triggers either a total thermonuclear disruption (Type Ia supernova, carbon-oxygen composition) or an accretion-induced collapse to a neutron star (oxygen-neon composition, via electron capture).

🎮 How to use

Increase mass directly with the slider, or use the accretion buttons to simulate a companion star feeding matter onto the white dwarf over time. Switch composition to compare carbon-oxygen and oxygen-neon white dwarfs, which have slightly different limiting masses and different collapse outcomes. Adjust surface temperature purely to change the star's visual colour, consistent with how white dwarfs cool over billions of years.

💡 Did you know?

Because Type Ia supernovae from carbon-oxygen white dwarfs reaching the Chandrasekhar limit explode with very consistent peak luminosity, they serve as "standard candles" for measuring cosmic distances — the same technique used to discover the accelerating expansion of the universe and dark energy in 1998.

Frequently asked questions

What is the Chandrasekhar limit?

The Chandrasekhar limit is the maximum mass, approximately 1.4 solar masses, that a white dwarf star can have while remaining supported by electron degeneracy pressure alone. Above this mass, the pressure from electrons packed as tightly as quantum mechanics allows can no longer counteract the star's own gravity, and the star must collapse or explode.

What is electron degeneracy pressure?

Electron degeneracy pressure arises from the Pauli exclusion principle, which forbids two electrons from occupying the same quantum state. Squeezed into the tiny volume of a white dwarf, electrons are forced into higher-momentum states purely because lower ones are already full, producing an outward pressure independent of temperature — quite different from the thermal pressure that supports ordinary stars.

Why does a white dwarf shrink as it gains mass?

Counterintuitively, adding mass to a degenerate star increases its density enough that gravity compresses it into a smaller volume, even though there is more material. This continues until, near the Chandrasekhar limit, the electrons become relativistic and the star's radius drops toward zero as gravity finally overwhelms degeneracy pressure.

What happens when a white dwarf crosses the Chandrasekhar limit?

The outcome depends on composition. A carbon-oxygen white dwarf typically ignites runaway carbon fusion throughout its volume, completely disrupting the star in a Type Ia supernova with no compact remnant. An oxygen-neon-magnesium white dwarf, however, can instead undergo electron capture onto neon and magnesium nuclei, removing the electrons that were providing pressure support and triggering a faster, quieter collapse directly into a neutron star — a process called accretion-induced collapse.

Is this simulation physically exact?

No. It uses a simplified, illustrative mass-radius formula and a compressed, dramatised timeline for the collapse sequence rather than a full stellar-structure calculation. The qualitative physics — degeneracy-pressure support, shrinking radius with mass, and the two distinct collapse channels for different compositions — reflects real astrophysics, but exact numerical details (timescales, exact limiting masses) are simplified for clarity.

⚙ Under the hood

Add mass to a white dwarf and watch it collapse into a supernova or neutron star once it crosses the Chandrasekhar limit.

white dwarfChandrasekhar limitstellar collapsesupernovastellar evolution

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install