How does a white dwarf supernova form?

In this type of supernova, a white dwarf in a binary star system gains mass from its companion. As its mass increases, the temperature and pressure within the white dwarf also increase, until nuclear fusion re-ignites at its center. read more

For them to become a type of supernova, extra mass must be transferred to them from a close companion star, via a stream of material that forms a flattened accretion disk about the white dwarf. This material slowly "drains" on to the surface of a white dwarf, and because of the degenerate nature of a white dwarf, the accumulated material can explosively ignite. read more

The theory of this type of supernova is similar to that of novae, in which a white dwarf accretes matter more slowly and does not approach the Chandrasekhar limit. In the case of a nova, the infalling matter causes a hydrogen fusion surface explosion that does not disrupt the star. read more

If the companion is another white dwarf instead of an active star, the two stellar corpses merge together to kick off the fireworks. This process is known as a double-degenerate model of a Type 1a supernova. read more