supernove

A supernova is a powerful stellar explosion that marks the end of a star’s life and can briefly outshine an entire galaxy. The event releases enormous energy and ejects newly synthesized elements into interstellar space, contributing to the chemical evolution of galaxies.

Supernovae are broadly classified into core-collapse events and thermonuclear (Type Ia) events. Core-collapse supernovae occur in massive stars, typically with more than about eight solar masses, when their iron cores collapse under gravity and a shock wave disrupts the star. Type Ia supernovae arise in binary systems when a white dwarf accretes matter from a companion and approaches a critical mass, triggering a thermonuclear runaway that destroys the star.

Observationally, Type II supernovae show hydrogen in their spectra, reflecting the outer hydrogen-rich envelopes of their progenitors, while Type Ia lack hydrogen and exhibit a distinctive silicon absorption feature near maximum light. Type Ibc supernovae (Ib and Ic) are core-collapse events that have lost most or all of their outer hydrogen and helium before exploding.

Supernovae are crucial for astronomy and cosmology. Type Ia supernovae serve as standard candles to measure cosmic distances and the expansion of the universe. All supernovae enrich the interstellar medium with heavy elements and can leave behind remnants such as neutron stars or black holes. Historical records include SN 1054 (Crab Nebula), SN 1572 (Tycho), and SN 1604 (Kepler), with modern observations capturing numerous events across the electromagnetic spectrum. Galactic rates are a few per century, with many more observed in other galaxies.