[AGarvin]

Hi Alex,

I wasn't quite sure what to say with such a large subject. I'm just an amateur astronomer too, I’ve just managed to accumulate papers, books and what not on this sorta stuff over the years. Hopefully I've got my facts correct (and not to may errors , it's been a while since I looked at this stuff). I don't know what your level of undertsanding is on stellar evolution so I thought a summary with some links would be a good start. I’ve used Wikipedia in most links as it was easier with everything in the one place.

A good start would be the Hertszprung-Russell diagram. In plots spectral type and luminosity class with temperature and luminosity. It also plots forming pre-main sequence T-Tauri and Herbig stars as they move down what are called the Hayashi and Henyey tracks, and older stars as they move off the main sequence along what are called the horizontal and asymptotic giant branches.

As for the actual fusion cycles; pre main sequence stars generally begin burning primordial deuterium (hydrogen-2) as they’re collapsing as deuterium fuses at a lower temperature than hydrogen-1. Along with the CNO cycle, the other main sequence cycle is the proton-proton cycle. Once this kicks in the star will be on the main sequence. There are four variations of this cycle, the PPI, PPII, PPIII and PPIV. Once a star run out of hydrogen and begins burning helium itmoves off the main sequence. The helium burns by the triple alpha process.

Stars smaller than about 8 solar masses go through a red giant stage and pretty much die at carbon ending up as white dwarfs. The smallest stars (red dwarfs) can theoretically end at the helium stage and leave behind a helium white dwarf, although I don’t think (?) the universe is old enough for any of these to have occurred yet. Larger stars become red supergiants and burn down through the elements; carbon and oxygen fuses with helium producing neon and magnesium down through silicon, sulphur and eventually iron, with each producing a burning shell around the core and feeding the shell below it. Since iron won’t fuse (unless energy is put into the system) the core ends up collapsing producing a supernova and leaving behind a neutron star, black hole or nothing at all. Elements heavier than iron are produced in the supernova explosion mainly by the neutron capture processes.

White dwarfs and neutron stars are supported from collapse by degeneracy pressure.

Hopefully this is the sort of thing you were after.

Andrew.