The Chandrasekhar Limit & Type Ia Supernovae: Observation, Measurement & Evidence

A Type Ia progenitor involves a white dwarf in a binary system gaining or merging mass under conditions that ignite carbon explosively. The precise progenitor channels include single-degenerate and double-degenerate pathways, and observations indicate that more than one route may contribute.

Type Ia spectra lack strong hydrogen in the defining classification and show products of thermonuclear burning. Their light curves are powered substantially by radioactive nickel and cobalt decay. Observed binary populations, supernova remnants, and nucleosynthetic yields constrain the possible progenitor pathways.

As a white dwarf becomes denser, electron speeds become relativistic and degeneracy pressure grows less effectively with further compression. If carbon ignites under degenerate conditions, rising temperature does not initially cause enough expansion to regulate the reaction. A thermonuclear runaway can burn a large fraction of the star and unbind it.

Type Ia spectra, light curves, radioactive nickel decay, remnants, and binary-population studies constrain explosion physics. Lack of a single universal companion signature supports multiple progenitor channels.