Type II Supernovae
Type II supernovae are even more powerful than type 1a—partly because they are derived from more massive stars, meaning more fuel for their explosions. Think nine times the mass of the Sun as a minimum.
As with type 1a supernovae, these explosions come about from the loss of balance, or hydrostatic equilibrium within the core of the star, from the thermal energy of the nuclear fusion pushing outwards and gravity pressing inwards. When all hydrogen is exhausted in the core, one side of the equation is gone, and the core collapses. Unlike with type 1a supernovae, this is enough to ignite the next densest fuel in the core, which then burns along merrily until it too is consumed and so on. During all this, the star remains relatively stable. This process is also occurring at various levels within the star, with progressively less dense fuels being burned as you move outwards from the core. Think onion thoughts.
This can happen multiple times until, at some point, the force from gravity is not enough to ignite the next stage of fusion, usually at the nickel-iron stage. At this point, the star suffers a critical core collapse, one with some pretty impressive displays of energy (and pretty complex thermodynamics.) Depending on the mass of the star, this can create either a neutron star or a black hole, the line between the two being set at twenty solar masses.
So, as you might guess, type II supernovae can't be used in the same manner as type 1a supernovae to calculate distance because the beginning mass (and thus the luminosity of the ending explosion) may vary so much.
There are few kinks left in this basic model that scientists haven't fully puzzled out yet. Keep a weather eye on the horizon for further developments as the required neutrino physics receives more research.
Check out the next page for the different types of type II supernovae, example pictures, information on type 1b and 1c, and more.