Minimum distance at which a large natural satellite can orbit its primary body without being torn apart by tidal forces.
If satellite and primary are of similar composition, the theoretical limit is about 2.5 times the radius of the larger body. The rings of Saturn , for example, lie inside Saturn's Roche limit and may be the debris of a demolished moon. The limit was first calculated by the French astronomer Édouard Roche (1820–53) in 1850.