Roche limit

The minimum distance from a larger body at which a smaller body can remain intact against tidal forces, given their densities and structural properties.

Tidal force: A difference in gravitational force across an extended object, caused by the gravity source being closer to one part than another. The larger body's force varies across the smaller body, producing the stress that can disrupt it.
Planetary rings: Disks of orbiting dust, ice, or rock particles surrounding a planet. Ring particles inside a planet's Roche limit may fail to accrete into a moon.
Density: Mass per unit volume of a substance or body. The classical Roche limit depends on the density ratio between satellite and primary.
Édouard Roche: A French astronomer and mathematician who studied the stability of satellites under tidal forces. His analysis gives the limit its name and its classical mathematical form.
Self-gravity: The gravitational attraction exerted by a body on its own material. It holds the smaller body together against the disruptive tidal force.
Saturn's rings: A broad system of icy and rocky rings orbiting Saturn. Much of the ring system lies within Saturn's Roche limit, where large moons cannot readily assemble.
Gravitational binding energy: The energy required to disperse a self-gravitating body into separated pieces. It measures how strongly gravity alone can resist tidal disruption.
Roche ellipsoid: An equilibrium shape of a synchronously rotating fluid body distorted by a larger body's gravity. It describes the deformation underlying Roche's fluid-satellite calculation.
Fluid Roche limit: The disruption distance for a fluid satellite whose shape can deform freely under gravity. It gives the classical Roche-limit estimate for bodies with negligible internal strength.
Phobos: The larger and innermost of Mars's two natural satellites. Its close orbit and tidal evolution are discussed in relation to Mars's Roche limit.

Linked from 26 pages