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planetplanet [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 the 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). Sections in this article: The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2007, Columbia University Press. All rights reserved. More on planet from Fact Monster:
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