# Roche limit

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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.

ee also

* Hill sphere
* Spaghettification (a rather extreme tidal distortion)
* Black hole

References

ources

* 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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### Look at other dictionaries:

• Roche limit — [rōsh] n. [after E. Roche (1820 83), Fr astronomer] the lowest possible altitude at which a natural satellite can form and orbit, withstanding the fragmenting force of the gravitational pull of a planet or other primary celestial body: see also… …   English World dictionary

• Roche limit — /rohsh/; Fr. /rddawsh/, Astron. the minimum distance below which a moon orbiting a celestial body would be disrupted by tidal forces or below which a moon would not have formed. [1885 90; named after French astronomer Édouard Roche (1820 83), who …   Universalium

• roche limit — ˈrȯsh , ˈrōsh noun or roche s limit shə̇z Usage: usually capitalized R Etymology: after E. A. Roche died 1833 French mathematician : the distance between a planet s center and its satellite within which the satellite cannot approach without… …   Useful english dictionary

• Roche limit — noun Etymology: E. A. Roche died 1883 French mathematician Date: 1889 the distance from a planet s center within which a satellite can neither approach nor reside without becoming disrupted by tidal forces …   New Collegiate Dictionary

• Roche limit — noun the closest distance which a satellite can approach its parent body without being pulled apart by tidal forces …   Wiktionary

• Roche Limit —    The minimum distance a satellite can orbit its parent planet without having tidal forces tear it apart …   The writer's dictionary of science fiction, fantasy, horror and mythology

• Roche lobe — Roche lobe, a gaseous bulge formed in binary stars by each star s gravitational pull on the other. ╂[< E. Roche; see etym. of Roche limit (Cf. ↑Roche limit)] * * * n. Astronomy either of two lobes that form an hourglass shaped volume of space… …   Useful english dictionary

• Roche — is French for boulder/rock . The word is (part of) several names: Business companies* Roche Applied Science, a business area of Roche Diagnostics, a division of Hoffmann–La Roche AG, Basel, Switzerland, one of the largest pharmaceutical companies …   Wikipedia

• Roche lobe — The Roche lobe is the region of space around a star in a binary system within which orbiting material is gravitationally bound to that star. If the star expands past its Roche lobe, then the material outside of the lobe will fall into the other… …   Wikipedia

• roche's limit — noun see roche limit * * * Roche s limit «R shihz, ROH », = Roche limit. (Cf. ↑Roche limit) …   Useful english dictionary