Roche Limit

12.2 Be able to identify the operation of each of the following interactions in the formation of planets and moons:
- a. the interaction between tidal gravitational and elastic forces to determine whether a body is broken apart (Roche Limit)

If a body such as a small moon approaches too near a larger planet it will be broken apart by tidal forces. The gravity of the invading object is not enough to hold it in one piece. Its remnants are likely to orbit the planet as ring. It is thought this is how most systems are formed.

The Roche limit is the name given to this distance which, depending on the density and mass of both objects is between 2 and 3 orbital radius of the planet and probably less for comets.

In 1994 Comet Shoemaker-Levy 9 was broken apart by the tidal forces it experienced when near Jupiter.