Virgin Galactic is developing a suborbital spacecraft to carry spaceflight participants to about 65 miles above Earth. The craft, SpaceShipOne, is carried high above the Earth by a special plane called The White Knight, then launched. Courtesy of Scaled Composites hide caption

toggle caption Courtesy of Scaled Composites

A National Science Foundation artist's drawing shows the inner four planets orbiting Gliese 581, a red dwarf star just 20 light-years from Earth. The newly discovered planet, in the foreground, has a 37-day orbit and, like Earth, is distant enough from the star for liquid water to exist. Lynette Cook hide caption

toggle caption Lynette Cook

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