Classification
As part of the attempt to understand supernovae, astronomers have classified them according to their light curves and the absorption lines of different chemical elements that appear in their spectra. The first element for division is the presence or absence of a line caused by hydrogen. If a supernova's spectrum contains lines of hydrogen (known as the Balmer series in the visual portion of the spectrum) it is classified Type II; otherwise it is Type I. In each of these two types there are subdivisions according to the presence of lines from other elements or the shape of the light curve (a graph of the supernova's apparent magnitude as a function of time).
| Type I No hydrogen |
Type Ia Presents a singly ionized silicon (Si II) line at 615.0 nm (nanometers), near peak light |
Thermal runaway | ||||||
| Type Ib/c Weak or no silicon absorption feature |
Type Ib Shows a non-ionized helium (He I) line at 587.6 nm |
Core collapse | ||||||
| Type Ic Weak or no helium |
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| Type II Shows hydrogen |
Type II-P/L/N Type II spectrum throughout |
Type II-P/L No narrow lines |
Type II-P Reaches a "plateau" in its light curve |
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| Type II-L Displays a "linear" decrease in its light curve (linear in magnitude versus time). |
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| Type IIn Some narrow lines |
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| Type IIb Spectrum changes to become like Type Ib |
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Read more about this topic: Super Nova