- Roche limit
If the primary is less than half as dense as the satellite, the rigid-body Roche Limit is less than the primary's radius, and the two bodies may collide before the Roche limit is reached.
How close are the solar system's moons to their Roche limits? The table below gives each inner satellite's orbital radius divided by its own Roche radius. Both rigid and fluid body calculations are given. Note Pan and Naiad in particular, which may be quite close to their actual break-up points.
In practice, the densities of most of the inner satellites of giant planets are not known. In these cases (shown in "italics"), likely values have been assumed, but their "actual" Roche limit can vary from the value shown.
Spaghettification(a rather extreme tidal distortion)
* Édouard Roche: "La figure d'une masse fluide soumise à l'attraction d'un point éloigné", Acad. des sciences de Montpellier, Vol. 1 (1847–50) p. 243
* [http://scienceworld.wolfram.com/physics/RocheLimit.html Detailed derivation of formulae for calculating the Roche limit]
* [http://www.merlyn.demon.co.uk/gravity5.htm#Roche Discussion of the Roche Limit]
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