Introductionplanet [Gr., = wanderer], a large nonluminous ball of rock or gas that orbits a star. The term, once limited to any of the eight solid, nonluminous bodies (major planets) that revolve around the sun, has been extended to include similar bodies discovered revolving around other stars. The term is sometimes used to include dwarf planets and asteroids (or minor planets) but excludes the other members of the solar system: comets and meteoroids (see meteor; see also planetary science and planetary system, as well as the table entitled Major Planets of the Solar System).
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