TypIaSupernovae

Type Ia supernovae are a class of stellar explosions resulting from the thermonuclear disruption of a carbon-oxygen white dwarf in a binary system. They are among the most luminous explosions observed and, unlike core-collapse supernovae, they typically show no hydrogen in their spectra.

Progenitors and explosion mechanisms: In leading models, the white dwarf gains mass from a companion star (single-degenerate channel) or merges with another white dwarf (double-degenerate channel). When the white dwarf approaches a critical mass, a thermonuclear runaway disrupts the star, synthesizing radioactive nickel-56 that powers the subsequent light output.

Observables and standardization: Type Ia light curves rise to a peak and then decline, with the rate of fading correlating with peak luminosity (the Phillips relation). This property makes them useful as standardizable candles for measuring cosmological distances. Spectroscopically, normal Type Ia events exhibit a prominent silicon absorption feature near maximum light and lack hydrogen or helium lines.

Diversity and subtypes: Most Type Ia supernovae are normal and calibratable for distance measurements, but several subtypes exist, including overluminous 91T-like and underluminous 91bg-like variants, as well as peculiar forms and events with circumstellar interaction. Ongoing research seeks to map the range of progenitor channels and how this diversity affects observable properties.

Scientific significance: Type Ia supernovae have been central to observational cosmology, underpinning measurements of the expansion rate of the universe and providing evidence for dark energy. They also contribute to understanding nucleosynthesis and the late stages of stellar evolution.

Environments and rates: They occur in both star-forming and quiescent galaxies, with rates dependent on the age and composition of the stellar population. Observational and theoretical work continues to refine progenitor scenarios and calibration methods.