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#1
2006-08-19, 10:42 AM
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太阳系新行星?
根据IAU(INTERNATIONAL ASTRONOMICAL UNION)
Q: Why is Pluto-Charon a “double planet” and not a “planet with a satellite”? A: Both Pluto and Charon each are large enough (massive enough) to be spherical. Both bodies independently satisfy the definition of “planet”. The reason they are called a “double planet” is that their common centre of gravity is a point that is located in free space outside the surface of Pluto. Because both conditions are met: each body is “planet-like” and each body orbits around a point in free space that is not inside one of them, the system qualifies to be called a “double planet.” 注册了Pluto-Charon.com 请大家评价,谢谢! 
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