Stars are born, they live, and they die.
Supernovae often leave remnant nebulae, and the Type II supernovae can leave a collapsed core in the form of a neutron star. There are many peculiar supernovae, including some that change type with time. It is helpful to classify the supernovae with both spectral and light curve information. With the diverse celestial zoo that exists, we should expect to see some unusual behavior from the supernovae. Type I supernova are characterised by the absence of hydrogen lines in their optical spectra.