<p><a href="https://en.wikipedia.org/wiki/Natural_satellite#Satellites_of_satellites" rel="nofollow">Wikipedia says there may be a reason (emphasis mine):</a></p>

<blockquote>
  <p>No "moons of moons" (natural satellites that orbit a natural satellite of another body) are currently known as of 2014. <strong>In most cases, the tidal effects of the primary would make such a system unstable.</strong></p>
</blockquote>

<p>This seems to be because the secondary would have to be very close to the primary - close enough that it doesn't become simply another satellite of the <em>actual</em> primary (i.e. the planet).</p>

<p>The page then goes on to talk about <a href="https://en.wikipedia.org/wiki/Rhea_(moon)" rel="nofollow">Rhea</a>, a moon of Saturn that may or may not have a ring system. <a href="http://www.sciencemag.org/content/319/5868/1380.abstract?maxtoshow=&amp;HITS=10&amp;hits=10&amp;RESULTFORMAT=&amp;fulltext=rhea&amp;searchid=1&amp;FIRSTINDEX=0&amp;resourcetype=HWCIT" rel="nofollow">This</a> gives some more information.</p>

CC BY-SA 3.0
2015-01-28T12:34:42.540Z
"Not known" does not mean impossible. Tidal effects of the primary can be quite small if it is far enough.
Envite
CC BY-SA 3.0
2015-01-27T18:14:44.117Z
2015-01-27T18:14:44.117Z
HDE 226868
<p>Is there an inherent instability or limit that prevents natural satellites like the moons of Jupiter from having their own natural satellites?</p>

<p>I looked at other questions such as <a href="https://astronomy.stackexchange.com/questions/856/do-moons-have-moons">do moons have moons</a> but they focus on discovery rather than theoretical limits analogous to the Roche limit for satellite formation.</p>

CC BY-SA 3.0
2015-01-27T18:13:01.727Z
I would say there isn't. The sun is a natural satellite of the Galactic Center. Jupiter is a natural satellite of the sun. Jupiter's moon is a natural satellite of Jupiter. Why not go another layer deeper?
Mathias711
CC BY-SA 3.0
2015-01-27T18:26:21.143Z
possible duplicate of [Do moons have moons?](http://astronomy.stackexchange.com/questions/856/do-moons-have-moons)
Florin Andrei
CC BY-SA 3.0
2015-01-27T18:31:18.520Z
Should be much easier in single lunar systems like Earth or Pluto, than in the well sorted Jupiter gravitational environment. The eccentricity of our Moon prevents any long-term stable orbits. But maybe Charon which is mutually tidally locked to Pluto could allow for it? And occasionally Earth captures an asteroid as a ["minimoon"](http://sservi.nasa.gov/articles/simulations-show-mini-moons-orbiting-earth). And many asteroids are binary, so...
LocalFluff
CC BY-SA 3.0
2015-01-27T23:39:52.837Z
While the proposed duplicate question is focused on discovery, both answers seem to address the question theoretically. You may want to be more specific what those answers are lacking, otherwise the questions are really too similar to be separated.
Mitch Goshorn
<natural-satellites>
Theoretical limits for natural satellites having natural satellites
Erik
# Theoretical limits for natural satellites having natural satellites

(Asked by: username_0 on 2015-01-27)

Is there an inherent instability or limit that prevents natural satellites like the moons of Jupiter from having their own natural satellites?

I looked at other questions such as [do moons have moons](https://astronomy.stackexchange.com/questions/856/do-moons-have-moons) but they focus on discovery rather than theoretical limits analogous to the Roche limit for satellite formation.

**Tags:** natural-satellites
> **Comments:**
> **username_1**: I would say there isn't. The sun is a natural satellite of the Galactic Center. Jupiter is a natural satellite of the sun. Jupiter's moon is a natural satellite of Jupiter. Why not go another layer deeper?  
> **username_2**: possible duplicate of [Do moons have moons?](http://astronomy.stackexchange.com/questions/856/do-moons-have-moons)  
> **username_3**: Should be much easier in single lunar systems like Earth or Pluto, than in the well sorted Jupiter gravitational environment. The eccentricity of our Moon prevents any long-term stable orbits. But maybe Charon which is mutually tidally locked to Pluto could allow for it? And occasionally Earth captures an asteroid as a ["minimoon"](http://sservi.nasa.gov/articles/simulations-show-mini-moons-orbiting-earth). And many asteroids are binary, so...  
> **username_4**: While the proposed duplicate question is focused on discovery, both answers seem to address the question theoretically. You may want to be more specific what those answers are lacking, otherwise the questions are really too similar to be separated.  

---

## 1 answers

### Answer by username_5 on 2015-01-27. Score: 2

[Wikipedia says there may be a reason (emphasis mine):](https://en.wikipedia.org/wiki/Natural_satellite#Satellites_of_satellites)

> No "moons of moons" (natural satellites that orbit a natural satellite of another body) are currently known as of 2014. **In most cases, the tidal effects of the primary would make such a system unstable.**

This seems to be because the secondary would have to be very close to the primary - close enough that it doesn't become simply another satellite of the *actual* primary (i.e. the planet).

The page then goes on to talk about [Rhea](https://en.wikipedia.org/wiki/Rhea_(moon)), a moon of Saturn that may or may not have a ring system. [This](http://www.sciencemag.org/content/319/5868/1380.abstract?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=rhea&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT) gives some more information.

> **Comments:**
> **username_6**: "Not known" does not mean impossible. Tidal effects of the primary can be quite small if it is far enough.  

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