Solar analog (–0.21) for solar twin. 16 Cygni B is sometimes noted as twin, but is part of a triple star system and is very old for a solar twin at over 9 Gyr. Another way of defining solar twin is as a "habstar" — a star with qualities believed to be particularly hospitable to an Earth-like planet. Qualities considered include variability, mass, age, metallicity, and close companions. The requirement that the star remain on the main sequence for at least 3 Ga sets an upper limit of approximately 1.5 solar masses, corresponding to a hottest spectral type of F5 V. Such
Tempe Terra Tempe Terra Tempe Terra is a heavily cratered highland region in the northern hemisphere of the planet Mars. Located at the northeastern edge of the Tharsis volcanic province, Tempe Terra is notable for its high degree of crustal fracturing and deformation. The region also contains a large number of small shield volcanoes, lava flows, and other volcanic structures. The region is named after the albedo feature "Tempe," first used by astronomer E.M. Antoniadi in 1930 to describe a bright patch of terrain centered near 40°N, 70°W. The name comes from the Vale of Tempe, a valley located south of Mount