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,
Sagan Planet Walk Sagan Planet Walk The Sciencenter's Sagan Planet Walk is a walkable scale model of the Solar System, located in Ithaca, New York. The model scales the entire Solar System—both planet size and distances between them—down to one five billionth of its actual size. Consisting of eleven obelisks situated along a path through the streets of downtown Ithaca, the Planet Walk leads from the Sun at Center Ithaca to Pluto at the Ithaca Sciencenter. The exhibition was originally created in 1997 in memory of Ithaca resident and Cornell Professor Carl Sagan. In 2012, the model was expanded to include a representation