Rocky extrasolar planet. Computer artwork of a planet discovered in August 2004. The planet is 50 light-years away, orbiting the star Mu Arae in the constellation of Altar. It is significant because, at 14 times the size of Earth, it is one of the smallest planets found outside our solar system. Scientists believe it is small enough to be rocky, but is unlikely to support life due to its proximity to the star; it is close enough to orbit it once every 10 days.