Starlight - Main Sequence - O - B - A - F - G - K - M - Luminosity Classes - Spectral Class Codes
G class main sequence stars are sun-sized. They fuse hydrogen slowly - their fuel will last for around ten billion years. Their surface temperature is around 5,000° K. Their radiation output is centered on the yellow region of the spectrum. The Sun is a G2V star. Alpha Centauri A is also a G2V star.
After they have exhausted their hydrogen fuel, they begin fusing helium. They then progress through a series of Red Giant stages. Much of their outer layers are dispersed in a planetary nebula. Finally, all that remains is a hot, extremely dense spent core - a White Dwarf.
