What's the Latest Development?
Since NASA's Kepler spacecraft was launched in 2009, it has discovered over 700 confirmed planets outside our solar system. The most promising planets are those which most resemble Earth, i.e. have about the same size, are made of rock and orbit in its star's habitable zone, where temperatures allow liquid water to be maintained. At the top of the list is Gliese 581g, a rocky planet just 20 light-years from Earth. "It's likely two to three times as massive as Earth and zips around its parent star, the red dwarf Gliese 581, every 30 days or so."
What's the Big Idea?
Discovered in February 2012, Gliese 667Cc orbits a red dwarf star some 22 light-years away, in the constellation Scorpius. "The alien world is a so-called 'super-Earth' that's at least 4.5 times as massive as our planet, and it completes an orbit every 28 days. At least one other planet resides in the 667C system." Third on the list is Kepler-22b, whose name is an homage to the craft that discovered it in December 2011. "If the greenhouse effect operates on Kepler-22b like it does on Earth, the alien world would have an average surface temperature of 72 degrees Fahrenheit (22 degrees Celsius), researchers have said."
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