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Supernovae come into two broad categories, called types, depending on the observed spectra. The two types also are theorized to be caused by different classes of stars with different mechanisms

  • Type I
    • The observed spectrum has no evidence of hydrogen
    • Origin: a white dwarf reaches the Chandrasekhar limit where electron degeneracy stops supporting gravitational collapse leading to thermonuclear runaway explosion
  • Type II
    • The observed spectrum has strong emission and absorption features due to hydrogen
    • Origin: a massive star (greater than 8 solar masses) ceases core-fusion when iron is produced, leading to gravitational collapse. The infalling matter (somehow) rebounds and causes the explosion (the how here is still being investigated)

Sub-types of each exist dependent on other elemental emission/absorptions observed in the spectra (e.g., Type Ib does not have the 635 nm silicon line whereas Type Ia does have that line) and the duration of the light curve.

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