Gliese 581g: A Little Taste of Home (or at Least Habitability)
By now, maybe you're getting a little homesick, or maybe you just need a survivable place to park while you work on repairs. We can't guarantee it'll provide much of a vacation spot, but at least in the Gliese 581 system you'll have your pick of two planets in the habitable zone: d and g. Habitable options around other stars include Gliese 667Cc, Kepler-22b, HD85512 b, Mars and, for a while at least, Earth [source: Torres].
As of February 2014, NASA's Kepler spacecraft has located 3,601 exoplanet candidates and confirmed 246. But few planets can compare to Gliese 581g in terms of human-friendliness. A rocky planet with a radius about 1.5 times that of Earth, it orbits closer to its star than we do, but remains in the habitable Goldilocks zone (neither too hot nor too cold for liquid water) because its red dwarf only pumps out about one-hundredth the solar energy our sun does. On the Earth Similarity Index measuring 0-1, it clocks in at around 0.92 – beating out former frontrunner Gliese 667Cc [sources: NASA; Torres].
Of course, it's not all beer and Skittles. Gliese 581g is tidally locked, meaning that the same hemisphere always faces its sun as it zips around its 37-day orbit (we hope you like birthdays and anniversaries). Just set your navigation system for the constellation Libra and make sure you've got enough fuel to make the 20-light-year jaunt [source: NASA].