How does a supernova occur?
A supernova is a powerful stellar explosion releasing enormous energy and ejecting material. Major pathways include massive-star core collapse and thermonuclear destruction in some white dwarfs. Not every star ends as a supernova.
Two major pathways
A massive stellar core can collapse when pressure support fails; shocks and neutrino interactions help eject outer layers. Type Ia events involve runaway nuclear reactions in a white dwarf under suitable conditions. Observational classification uses spectral features and is not identical to a classification by physical mechanism. Models are tested using several kinds of observation.
Elements and remnants
Ejected matter enriches interstellar material and influences later generations of stars. Core collapse can leave a neutron star or black hole, whereas thermonuclear outcomes differ. Corrected Type Ia light curves help measure cosmic distances, but their luminosities are not perfectly identical. Expanding remnants can remain observable long after the brief bright explosion phase.