Types of Supernovas

Supernovas are divided into classes based upon the appearance of their spectra: hydrogen lines are prominent in Type II supernovas; hydrogen lines are absent in Type Ia supernovas.

This tells us that the progenitor stars either had hydrogen in their outer envelopes or did not have hydrogen in their outer envelopes. Type II supernovae are associated with massive stars while Type Ia supernovae may be associated with white dwarf binary star systems, where an accreting white dwarf is driven above the Chandrasekhar Mass Limit and the white dwarf collapses and explodes.

Supernova Remnants

The outer layers of the exploding star are initially carried outward at speeds of 10,000-20,000 km/s--a tremendous amount of energy. The expanding material (ejecta) shocks and heats the gas which surrounds the supernova which produces intense emission producing a Supernova Remnant. As the ejecta moves outward, it sweeps up, as well as shocking and heating the surrounding gas. This slows down the ejecta (shell). After tens or hundreds of thousand years, the expanding ejecta eventually slows to the point where it merges with the ISM ending the life of the supernova remnant evolution.