出典:Wiktionary
出典:Wikipedia
出典:『Wikipedia』 (2011/05/30 17:37 UTC 版)
An astronomical body's Hill sphere is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sphere of its own. Any object within that distance would tend to become a satellite of the moon, rather than of the planet itself.