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
Lada Terra remnants. The most prominent region is the midlands, where gently sloping topography is disrupted by faults, fractures, and corona, making this area the most complex and studied region in Lada Terra. The western portion of Lada Terra contains a large dome-shaped structure about across termed, "the Lada Rise," which is the main highland of the region. It reaches an elevation of about and is dominated by one of the most massive corona in the solar system, the Quetzalpetlatl Corona, as well as two massive rift zones surround and partially intersect the rise. The high rises of Venus generally fall into