There are two basic classes, Type I and Type II, and there are also a handful of sub-classes that have to do with the differences in the heavy element abundances within the progenitor star that exploded, or in specific features in the spectra of the supernova outburst. Massive stars are the dominant source, and so most supernovae involve very young, massive stars less than a billion years old. These are mostly found in spiral-type galaxies. The Type Ia involve the detonation of a white dwarf in a binary system. The companion star dumps lots of mass on the white dwarf which then exceeds its Chandrasekhar Limit of 1.4 solar masses and detonates. These can be caused by very old stars 5-10 billion years old. These are very abundant in elliptical galaxies. The above image is of the ring-like ejecta from supernova SN1987A as seen in 1994.
The classes are distinguished based on their different 'light curves' ( how the brightness of the supernova changes in time after the explosion) and radio/optical properties. The best list I have seen is at Michael Richmond's SN Taxonomy page
very approximately:
Type 1a No Hydrogen Accreting white dwarf Type 1b No hydrogen Massive star Type 1c No Hydrogen/helium Massive star Type II-p Hydrogen Massive red supergiant Type II-l Hydrogen Less-massive supergiant Type IIb Hydrogen/helium Massive star Type IIn Hydrogen Massive star/slow decline
Copyright 1997 Dr. Sten Odenwald Return to Ask the Astronomer.