Chandrasekhar limit

Physical origin and characteristics

White dwarfs are compact stellar remnants held up by the quantum-mechanical pressure of electrons (electron degeneracy pressure). As a white dwarf becomes more massive its electrons are forced into higher momentum states; when their speeds approach the speed of light the pressure no longer increases rapidly enough to resist gravity. This relativistic regime produces a limiting mass. The limit depends weakly on the chemical composition through the mean molecular weight per electron: for heavier nuclei the numerical value shifts somewhat from the canonical figure.

Consequences and examples

Crossing the Chandrasekhar limit has important astrophysical outcomes. A white dwarf approaching the limit by accretion from a companion star or by merger with another white dwarf can ignite thermonuclear runaway and produce a Type Ia supernova. In other pathways, loss of pressure support leads to catastrophic collapse into a neutron star or, for sufficiently large mass and compactness, a black hole.

• Mass–radius relation: more massive white dwarfs are smaller; near the limit the radius tends toward zero in simple models.
• Type Ia supernovae: explosions associated with white dwarfs that reach conditions near this mass are major distance indicators in cosmology.
• Threshold for further collapse: objects above the limit are candidates to become neutron stars or black holes after collapse.

Historical development

The limit was derived in detail by the Indian astrophysicist Subrahmanyan Chandrasekhar in the early 1930s, building on prior work about degenerate matter and stellar structure. His calculation showed how special relativity alters the pressure–density relation and leads to a fixed mass ceiling. The result met resistance from established scientists at the time, but subsequent theoretical and observational work confirmed its importance. Chandrasekhar received widespread recognition for his contributions to stellar physics.

Notable facts and further context

The Chandrasekhar limit is often cited as roughly 1.4 solar masses; this is a representative value for common white-dwarf compositions. Precise limits vary with composition and improved physics such as general relativistic corrections, rotation, magnetic fields, or temperature effects. Modern studies of compact objects take these refinements into account when predicting outcomes of stellar evolution and binary interactions.

For additional reading about the limit and related topics see maximum mass, the physics of white dwarfs, stellar structure and evolution reviews, biographical material on Subrahmanyan Chandrasekhar, and his collected papers works. Observational links include the Sun as a mass reference solar mass, the fate of collapsing remnants like neutron stars, and the possibility of forming black holes.