Evolution of a G star.
A G star is a yellowish star of spectral type G, with a surface temperature in the range 5,000 to 5,800°C and mass of 0.8 to 1.1 solar masses. G stars have spectra containing many absorption lines of neutral and ionized metals, together with some molecular absorption bands. The H and K lines of ionized calcium are particularly strong.
G-type giant stars, such as Capella, are slightly cooler but more luminous than their main sequence counterparts, while G-type supergiants have a mass of 10 to 12 solar masses and a luminosity of 10,000 to 300,000 times that of the Sun.