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
Terra: The Nature of Our World previous podcasts. LifeOnTERRA's ("TERRA: The Nature of Our World's") website http://www.lifeonterra.com/ was launched in October 2006. This site features a new biweekly episode ready for viewing and downloading, along with its 8 seasons of documentary offerings. All videos are offered as QuickTime (.m4v). The current website was launched in September 2013 and includes many features from the previous website, with a fresh new look. The website was designed and built by Jeff Reed. Hosting for the Videos is provided by Vimeo. As - TERRA: The Nature of Our World-www.lifeonterra.com is the winner of two 2013 WEBBY awards, the People's Voice