<p>Would it be possible for two planets orbiting around each other to share a moon that orbits both separately? Would the moon in question would do something akin to a large figure 8 as it orbited both or would this be possible in the first place?</p>

<p>Also, what effects might we see on the planets because of this?</p>

<p>(Side note: This stems from a Worldbuilding question, but I figured I would ask the astronomy question on the Astronomy StackExchange)</p>

CC BY-SA 3.0
2017-07-25T22:52:07.680Z
A figure-8 orbit is possible, but it's only stable if the 3 bodies have almost identical masses. See     http://tuvalu.santafe.edu/~moore/gallery.html and the linked articles there for details.
PM 2Ring
CC BY-SA 3.0
2017-07-26T03:05:43.240Z
Despite the comment above saying it's possible, it's really not, not long term.   3 body systems are chaotic.   Objects can orbit a single object or more distantly orbit a binary system - like Pluto/Charon's moons.   But a figure 8 orbit, while it can be worked out mathematically to almost work if conditions are just right, it's really not possible for any lasting period of time.
userLTK
CC BY-SA 3.0
2017-07-26T07:27:55.613Z
Also keep in mind you're really dealing with at least a four body system when you add a star for the planets to orbit.  That's going to increase instability of the moon's orbit as would any other bodies in the system.
StephenG - Help Ukraine
<orbit><gravity>
Shared moon in a double planet system
JustSnilloc
# Shared moon in a double planet system

(Asked by: username_0 on 2017-07-25)

Would it be possible for two planets orbiting around each other to share a moon that orbits both separately? Would the moon in question would do something akin to a large figure 8 as it orbited both or would this be possible in the first place?

Also, what effects might we see on the planets because of this?

(Side note: This stems from a Worldbuilding question, but I figured I would ask the astronomy question on the Astronomy StackExchange)

**Tags:** orbit, gravity

> **Comments:**
> **username_1**: A figure-8 orbit is possible, but it's only stable if the 3 bodies have almost identical masses. See     http://tuvalu.santafe.edu/~moore/gallery.html and the linked articles there for details.  
> **username_2**: Despite the comment above saying it's possible, it's really not, not long term.   3 body systems are chaotic.   Objects can orbit a single object or more distantly orbit a binary system - like Pluto/Charon's moons.   But a figure 8 orbit, while it can be worked out mathematically to almost work if conditions are just right, it's really not possible for any lasting period of time.  
> **username_3**: Also keep in mind you're really dealing with at least a four body system when you add a star for the planets to orbit.  That's going to increase instability of the moon's orbit as would any other bodies in the system.  

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