So I have a fictional world where I have three moons orbiting this planet. I've used this web site to try and figure this out but I wanted to ask this question myself.

My planet (a little bigger then earth) had 3 small moons orbiting it, (they are about the size of Uranus' moon Oberon) and they had a tidal lock to the planet and each moon was equally spaced around the planet in their orbit and they shared a more or less same orbit pattern. Would that be possible? And how would that affect the ocean/land of the planet? So far the planet is a good deal covered with ocean with a ring of continents.

  • $\begingroup$ Are they different distances? In that case, it is unlikely that they will travel the same 'speed' around your planet. Or does your story assume they're in the same orbit, just at three different spaces (also problematic, but we can try to help). $\endgroup$
    – Mikey
    Commented Aug 1, 2015 at 5:39
  • $\begingroup$ I didn't think about speed actually. But it is a good point to bring up. I kind of wanted an aesthetic where you would have all three moon go across the sky over the course of one night. So you would see one moon leaving as another enters. I suppose that would mean that they are going pretty fast. $\endgroup$ Commented Aug 1, 2015 at 18:52
  • $\begingroup$ this would mean they have very specific orbital planes. If they're the same side and a consistent 'procedural $\endgroup$
    – Mikey
    Commented Aug 1, 2015 at 23:02
  • $\begingroup$ The orbital period of a moon is dependent on the mass of the central planet and the distance from that planet. So unless they share the same orbit (in which case they will be unstable, unless they are too small to influence each other gravitationally) they will have different orbital periods. $\endgroup$ Commented Apr 14, 2016 at 13:20

2 Answers 2


With the number of moons you have in your planetary system, I doubt you'd be able to maintain tidally locked moons. Our moon stays tidally locked to us because there aren't any big, nearby objects to add a little extra torque to tidally unlock our moon.

There's a "game" on Steam called "Universe Sandbox 2" that will allow you to build and experiment with your own planetary and solar systems. This may be really helpful for furthering your intuitive feel for what will work and what won't.

  • $\begingroup$ Thank you for the suggestion and i will definitely look into it once the game becomes available. right now the game is only available in alpha and hasn't been released on steam yet. I look forward to it though. $\endgroup$ Commented Aug 1, 2015 at 4:22
  • $\begingroup$ @CreativeCrusader sorry about that. I own the first game and saw videos for the second and assumed it had been released. $\endgroup$
    – Green
    Commented Aug 1, 2015 at 5:18
  • $\begingroup$ Lol the release says to be the summer of 2015 so it shouldn't be too much longer now. $\endgroup$ Commented Aug 1, 2015 at 18:49

Oberon is not only smaller than Diana, it is much less dense. Even it we assume roughly the same density as Diana instead, the three moons still only have just under a quarter of the volume. Less volume equals less mass and less gravitational pull. So if your planet was larger than Earth, its three moons would have a much more difficult time locking its axis of rotation. The wobbling axis of rotation would tend to produce wild storms.

With three moons pulling them, the tides with be much more frequent. But again, thanks to the decrease in mass/gravitation, those tides would be much smaller.

And since they have a much smaller surface area, the moons would provide less protection. Expect a lot more cosmic debris to smash into your planet.

As for the three sharing an orbital path, it is possible (if highly unlikely), so long as they are nearly identical in size and mass.


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