a nonluminous celestial body larger than an asteroid or a comet,illuminated by light from a star,such as the sun,around which it revolves. In the solar system there are nine known planets: Mercury,Venus,Earth,Mars,Jupiter,Saturn,Uranus,Neptune,and Pluto
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- 行星，比一颗小行星或一颗彗星大的不发光的天体，由它绕转的恒星，如太阳的光所照亮在太阳系中有九个已知的行星：水星、金星、地球、火星、木星、土星、天王星、海王星和冥王星
