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Twenty Light-years away, a veritable "Stone's throw" in an astronomical sense, lies Gliese 581, and the fourth planet, dubbed Gliese 581d (They're astronomers, not writers) is (one of several actually, but this is the interesting one) a planet that falls into the habitable zone for it's star.
FrenchAstronmers said:
"With a dense carbon dioxide atmosphere - a likely scenario on such a large planet - the climate of Gliese 581d is not only stable against collapse but warm enough to have oceans, clouds and rainfall,"
Gliese 581d is believed to have a mass around 7times that of Earth, but a lower rotational velocity results in a gravity of about twice that of Earth.
FrenchAstronmers said:
"The denser air and thick clouds would keep the surface in a perpetual murky red twilight, and its large mass means that surface gravity would be around double that on Earth,"
Two things strike me as peculiar, first has already been said, this Planet is actually very close to us. While it would still take 300,000Years to arrive using conventional propulsion, on a cosmic scale, it might as well be down the block.
Second, Gliese581(The star) is a Red Dwarf (Tiny, with low output), Red Dwarf stars are not exactly the powerhouse of fusion our Star is, it was originally thought that the likeihood of planets forming within a Red Dwarfs theoretical habitation zone was beyond unlikely, and damn near impossible, once again showing the world, that when dealing with things on a galactic scale, there's no such thing as a statistical impossibility.
It's just a shame Obama pretty much shut down our space program.