Supernovae result from the explosive death of a star and are classified as two types. Type Ia supernovae occur in binary star systems in which gas from one star falls onto a white dwarf with a mass close to the Chandrasekhar critical mass and causes it to explode (like in this graphic). The explosion is caused by the ignition of runaway thermo-nuclear reactions under degenerate matter conditions. Type II supernovae occur in stars at least ten times more massive than our Sun, which suffer runaway thermo-nuclear reactions at the end of their lives, leading to explosions. Such explosions can be either total (no solid remnant) or may leave behind a rapidly spinning neutron star (a pulsar) or a black hole. Note how, in this simulation, the secondary star survives the detonation of the white dwarf and is thrown away like a slingshot. It picks up a rotation about its axis, since it was locked into a rotation about the white dwarf before it exploded. The supernova remnant (the dust cloud that expands from the explosion) remains for many years. The flash only lasts a few seconds.
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