A star of spectral type G, which includes the Sun. G-type stars on the main sequence have temperatures of 5300–6000 K, and therefore appear yellow. G-type giants are about 100–500 K cooler than main-sequence stars. G-type supergiants are about 4500–5500 K. The spectrum of the Sun (type G2) is dominated by lines of singly ionized calcium (principally the H and K lines) and neutral metals. In cooler G stars the molecular bands of CH and CN become visible. Main-sequence G stars, and giants such as Capella, have masses of 0.8–1.1 solar masses, while supergiants are of 10–12 solar masses. The luminosities of G-type giants are about 30–60 times the Sun's, and for supergiants 10 000–300 000 times the Sun's.
Subjects: Astronomy and Astrophysics.