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a celestial body that orbits the sun, is round because of it's own gravity, and has cleared the neighborhood around its orbital path

solar system

the sun and all of the planets and other bodies that travel around it


a natural or artificial body that revolves around a celestial body that is greater in mass


the change in the illuminated area of one celestial body as seen from another celestial body; phases of the moon are caused by the positions of Earth, the sun, and the moon


an event in which the shadow of one celestial body falls on another

terrestrial planet

one of the highly dense planets nearest to the sun; Mercury, Venus, Earth, and Mars


the portion of Earth that is water


a small, rocky, object that orbits that sun; most asteroids are located in a band between the orbits of Mars and Jupiter

dwarf planet

a celestial body that orbits the sun, is round because of its own gravity, but has not cleared its orbital path

gas giant

a planet that has a deep, massive atmosphere, such as Jupiter, Saturn, Uranus, or Neptune

nebular hypothesis

a model for the formation of the solar system in which the sun and planets condense from a cloud (or nebula) of gas and dust


a large cloud of dust and gas interstellar space; a region in space where stars are born


a small body of ice, rock, and cosmic dust that follows an elliptical orbit and that gives off gas and dust in the form of a tail as it passes close to the sun


a planet like body that orbits a star other than the sun

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