How do white dwarfs form?
A white dwarf is a dense core left after the evolution of a low- or intermediate-mass star such as the Sun. After outer layers are lost, the remnant can be roughly Earth-sized. It is a late stage of an earlier star rather than the birth of an ordinary small star.
What supports the remnant?
Electron degeneracy pressure provides essential support, rather than ordinary hot-gas pressure alone. A typical white dwarf lacks sustained core hydrogen fusion like that of a main-sequence star. It radiates stored heat and cools. Greater mass generally corresponds to a smaller radius, unlike familiar everyday objects. Stable white dwarfs also have an upper mass limit.
Different outcomes in binary systems
Accretion from a companion or merger with another white dwarf can lead to different explosive outcomes, but not every white dwarf becomes a supernova. Surface nova eruptions must be distinguished from destructive Type Ia explosions. Cooling models help investigate stellar-population ages. White dwarfs also differ from neutron stars in density, support mechanisms, and formation pathways.