Solar System largely of materials with lower melting points. The boundary in the Solar System beyond which those volatile substances could condense is known as the frost line, and it lies at roughly 5 AU from the Sun. The objects of the inner Solar System are composed mostly of rock, the collective name for compounds with high melting points, such as silicates, iron or nickel, that remained solid under almost all conditions in the protoplanetary nebula. Jupiter and Saturn are composed mainly of gases, the astronomical term for materials with extremely low melting points and high vapour pressure, such as hydrogen, helium,
Sun Dutch "zon", Old High German "sunna", modern German "Sonne", Old Norse "sunna", and Gothic "sunnō". All Germanic terms for the Sun stem from Proto-Germanic *"sunnōn". The Latin name for the Sun, "Sol", is used at times as another name for the Sun, but is not commonly used in everyday English. "Sol" is also used by planetary astronomers to refer to the duration of a solar day on another planet, such as Mars. The related word "solar" is the usual adjectival term used for the Sun, in terms such as solar day, solar eclipse, and Solar System. A mean Earth solar