According to current theory, two different mechanisms produce
supernovae: First, stars considerably more massive than our Sun
can most probably not evolve quietly into an end state as a
white dwarf. When coming to age, these massive stars explode in
a most violent detonation which flashes up at a luminosity of up
to 10 billion times that of the sun, called supernova (of type
II, or Ib or Ic), and ejecting the very greatest part of the
stellar matter in a violently expanding shell. These explosions
are thought to leave a compact remnant, such as a neutron star.
Aternatively, infalling matter on a white dwarf star can cause
it to explode as a supernova of type Ia; these events do
probably not leave a stellar remnant. The classification of
supernovae in types was introduced by Rudolph Minkowski
(Minkowski 1941) on the grounds of their spectra: Type I
supernovae show no hydrogen lines in their spectra, whereas
these lines are present in those of Type II. Later these types
were subdivided, again based on their spe