Type Ia supernova

A type Ia supernova is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Physically, carbon-oxygen white dwarfs with slow rotation are limited to below 1.44 solar masses. 
Since type Ia supernovae have a known brightness they can be used as standard candles to determine the distance to a galaxy once the stretch-factor is accounted for. 
When a runaway thermonuclear explosion rips through a white dwarf star and blows the star to bits, it is called a type 1a supernova. These explosions are incredibly violent and incredibly bright, sometimes outshining entire galaxies.
Type I (especially Ia) supernova create most of the iron and nickel found in the interstellar medium. Type 1a supernovae are several times more luminous than type Ib, Ic, and type II supernovae. They leave no core remnant behind, and happen when a low-mass star's core remnant (a white dwarf) detonates.