Types Of Supernova    

                                    Type II Supernovae

A humongous stellar explosion, a supernova, may be brighter than an entire galaxy for a brief time. It may be silent, but it sure is bright! The light that travels away from a supernova can be read by specialized detectors here on Earth to produce a spectrum, which for this lesson's purposes can be remembered as an arrangement of colors in order of wavelength.

A spectrum may have added or missing lines of colors that clue astronomers into the different compositions of matter from which the lights came or passed through. And by 'composition,' I mean the stuff the star is made of. It's like a barcode on a product label that tells a machine what the product actually is. In our case, when a massive star is days away from a supernova explosion, it is composed of a lot of different things, from hydrogen at the very outer layers to iron at its very core.
Most stars that are eight or more times the mass of our sun die as a Type II Supernova. A Type II Supernova is a supernova that is classified as having hydrogen lines in its spectra that are made by the explosion of a very large star. The hydrogen lines come from the hydrogen-rich outer layers of the star as the star explodes.

                                      

                    Type Ia Supernovae

But there are other kinds of supernovae. A Type I Supernova is a kind of supernova with no hydrogen lines in its spectrum. How can this occur if I just said that the outer layers of the star are rich in hydrogen? Well, there are two ways. The first is a supernova explosion that results from the collapse of a white dwarf, termed a Type Ia Supernova. A white dwarf is a remnant of a star that wasn't massive enough to force the ignition of carbon fusion for energy.

To understand how a Type Ia Supernova occurs, you also need to know a term called the Chandrasekhar Limit. The Chandrasekhar Limit is equal to about 1.4 solar masses, and it tells us that all stable white dwarfs must be smaller than 1.4 solar masses. This means stars more massive than 1.4 solar masses can only become white dwarfs if they shed mass as they evolve, and we know this does occur and helps to explain why medium mass stars upwards of eight solar masses can become white dwarfs.