<p>I would imagine that in most cases the sub satellite would be inside the instability limit of the planetary system in question and that such a scenario would be unstable. It would be interesting to model this with a simple 3-body system to see how the sub-satellite behaved over time (assuming a rigid body to start out). Someone else mentioned tidal perturbations and surely those would play a significant role too.</p>

CC BY-SA 4.0
2019-02-18T19:13:41.533Z
2019-02-18T19:13:41.533Z
PSR-1937-21
<p>As far as I understand, a moon is an object in permanent orbit around a planet, dwarf-planet, asteroid, etc. If there was another object permanently orbiting this moon, would that be a moon-moon?</p>

<p>Is there any natural object of such kind that we know of?</p>

<p>If no, why are such objects so unlikely?</p>

<hr>

<p>Edit: this is question is different from <a href="https://astronomy.stackexchange.com/q/856/24789">Do moons have moons?</a> because I explicitly ask for a reason. Also, the terminology is included here.</p>

CC BY-SA 4.0
2019-02-17T11:31:08.243Z
Similar, not exactly the same question here:   https://astronomy.stackexchange.com/questions/856/do-moons-have-moons
userLTK
CC BY-SA 4.0
2019-02-18T11:35:53.813Z
@userLTK thanks for this hint, the answer given there is very comprehensive.
Everyday Astronaut
CC BY-SA 4.0
2019-02-18T12:43:41.900Z
I reckon the most likely candidates for moons to be orbited by a sub-moon would be Titan, Luna, and Triton. Perhaps also Callisto, but despite the high mass not Ganymede, because of its quite close orbit around the massive Jupiter and strong gravitational interaction with Europa.
leftaroundabout
CC BY-SA 4.0
2019-02-18T21:54:13.770Z
I'm voting it's a duplicate, as the answers there are comprehensive and address *all the questions asked here* (except the one about calling it a moon-moon, which I'm taking as rhetorical humour). rehctawrats, your edit changes nothing.
Chappo Hasn't Forgotten
<orbit><natural-satellites>
Is there any known moon of a moon?
Everyday Astronaut
# Is there any known moon of a moon?

(Asked by: username_0 on 2019-02-17)

As far as I understand, a moon is an object in permanent orbit around a planet, dwarf-planet, asteroid, etc. If there was another object permanently orbiting this moon, would that be a moon-moon?

Is there any natural object of such kind that we know of?

If no, why are such objects so unlikely?

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Edit: this is question is different from [Do moons have moons?](https://astronomy.stackexchange.com/q/856/24789) because I explicitly ask for a reason. Also, the terminology is included here.

**Tags:** orbit, natural-satellites

> **Comments:**
> **username_1**: Similar, not exactly the same question here:   https://astronomy.stackexchange.com/questions/856/do-moons-have-moons  
> **username_0**: @username_1 thanks for this hint, the answer given there is very comprehensive.  
> **username_2**: I reckon the most likely candidates for moons to be orbited by a sub-moon would be Titan, Luna, and Triton. Perhaps also Callisto, but despite the high mass not Ganymede, because of its quite close orbit around the massive Jupiter and strong gravitational interaction with Europa.  
> **username_3**: I'm voting it's a duplicate, as the answers there are comprehensive and address *all the questions asked here* (except the one about calling it a moon-moon, which I'm taking as rhetorical humour). rehctawrats, your edit changes nothing.  

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## 1 answers

### Answer by username_4 on 2019-02-18. Score: 3

I would imagine that in most cases the sub satellite would be inside the instability limit of the planetary system in question and that such a scenario would be unstable. It would be interesting to model this with a simple 3-body system to see how the sub-satellite behaved over time (assuming a rigid body to start out). Someone else mentioned tidal perturbations and surely those would play a significant role too.


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