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Roche limit (far away sphere)
Consider an orbiting mass of fluid held together by gravity, here viewed from above the orbital plane. Far from the Roche limit the mass is practically spherical.
Roche limit (tidal sphere)
Closer to the Roche limit the body is deformed by tidal forces.
Roche limit (ripped sphere)
Within the Roche limit the mass's own gravity can no longer withstand the tidal forces, and the body disintegrates.
Roche limit (top view)
Particles closer to the primary move more quickly than particles farther away, as represented by the red arrows.
Roche limit (ring)
The varying orbital speed of the material eventually causes it to form a planetary ring

The Roche limit (pronounced /ˈroʊʃ/), sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction. Inside the Roche limit, orbiting material will tend to disperse and form planetary rings, while outside the limit, material will tend to coalesce. The term is named after Édouard Roche, the French astronomer who first calculated this theoretical limit in 1848.

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