Summary
White dwarfs are stars that have burnt up all of the hydrogen they once used as fuel. The inward push of gravity is balanced by electron degeneracy pressure. Fusion in a white dwarf’s core produces outwards pressure, which is balanced by the inward push of gravity due to the star’s mass. A type Ia supernova occurs when a white dwarf in a binary star system goes over the Chandrashekhar limit due to accreting mass from or a merger with its companion star.