What is the difference between a Type II supernova and a Type III supernova?

A supernova is a powerful and luminous explosion that occurs when a star runs out of fuel and collapses. There are different types of supernovae, classified according to the elements found in their spectra and the way they decline after reaching peak luminosity. Two main types of supernovae are Type II and Type III, also known as core-collapse supernovae.

Type II supernovae happen when a massive star, more than eight times the mass of the Sun, exhausts its fuel and its core collapses, producing a neutron star or a black hole. Type II supernovae are characterized by the presence of hydrogen lines in their spectra and a gradual decline after reaching peak brightness.

Type III supernovae, on the other hand, are produced by the core collapse of a star with a mass greater than about 20 times that of the Sun. Unlike Type II supernovae, Type III supernovae show no hydrogen lines in their spectra and have a much faster decline rate after peak luminosity.