planet

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planet (Gk. ‘wandering star’) Large, non-stellar body in orbit around a star, shining only by reflecting the star's light. Planets may be either rocky in composition, such as Mercury, Venus, Earth and Mars, or mainly gaseous, such as Jupiter, Saturn, Uranus and Neptune. In our Solar System there are nine major planets, together with thousands of asteroids or minor planets. In the 1990s astronomers confirmed the first extra-solar (outside our Solar System) planets. In 1995 scientists discovered the first planet (51 Pegasi b) orbiting a main-sequence star, 51 Pegasi, similar to our Sun. By 2002 astronomers had discovered 101 extra-solar planets. See also Pluto

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