The Sun is a G2 star, containing 99.8% of the Solar System's mass. It has a diameter of 1,390,000 km and a mass of 1.1989 x 10^30 kg. The surface temperature is 5800 K, and the core is 15,600,000 K. Its chemical composition includes 92.1% hydrogen and 7.8% helium. Energy production in the core involves hydrogen fusion.