Planet smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded
Dark Planet the series' best. It was part of a second set of four books, which were successful enough to allow the range to continue. Dark Planet "Dark Planet" is a BBC Books adventure book written by Davey Moore and is based on the long-running British science fiction television series "Doctor Who". It features the Tenth Doctor and Martha. This one was set on a future version of Earth where society was split in half and some people stayed underground and the rest high above on land dangerously close to the Sun. This is part of the "Decide Your Destiny" series which