Roche limit

[2] The Roche limit typically applies to a satellite's disintegrating due to tidal forces induced by its primary, the body around which it orbits.

Some real satellites, both natural and artificial, can orbit within their Roche limits because they are held together by forces other than gravitation.

Objects resting on the surface of such a satellite would be lifted away by tidal forces.

These two rings could possibly be remnants from the planet's proto-planetary accretion disc that failed to coalesce into moonlets, or conversely have formed when a moon passed within its Roche limit and broke apart.)

The gravitational effect occurring below the Roche limit is not the only factor that causes comets to break apart.

At one extreme, a completely rigid satellite will maintain its shape until tidal forces break it apart.

At the other extreme, a highly fluid satellite gradually deforms leading to increased tidal forces, causing the satellite to elongate, further compounding the tidal forces and causing it to break apart more readily.

For example, a rubble-pile asteroid will behave more like a fluid than a solid rocky one; an icy body will behave quite rigidly at first but become more fluid as tidal heating accumulates and its ices begin to melt.

The Roche limit is also usually calculated for the case of a circular orbit, although it is straightforward to modify the calculation to apply to the case (for example) of a body passing the primary on a parabolic or hyperbolic trajectory.

Irregular shapes such as those of tidal deformation on the body or the primary it orbits are neglected.

A more accurate approach for calculating the Roche limit takes the deformation of the satellite into account.

For instance, comet Shoemaker–Levy 9's decaying orbit around Jupiter passed within its Roche limit in July 1992, causing it to fragment into a number of smaller pieces.