The distance from the centre of a planet within which any large satellite would be torn apart by tidal forces. The Roche limit lies at approximately 2.46 times the planet’s radius, if the planet and satellite have similar densities. Within the limiting distance no major satellite could form, although small, strong objects such as artificial satellites can survive well within this distance. All four major planets have ring systems within the Roche limit. It is named after the French mathematician Édouard Albert Roche (1820–83).