Would it ever be possible for two planets to share a moon? If so, how would it have to work?

Answer 1

this cannot be done. a moon must have a defined orbit around a planet, there can't be a combination of orbits of two planets that can allow a moon to have a defined orbit around the two of them.

Answer 2

Yes, that's definetely very possible.

The proof lies in the binary star system. In a binary star system there are two suns, with planets circling both suns together, as the suns circle each other. Make sense?

A pair of planets would have to be joined in a close-revolving single orbit around the sun (or suns, if you want). what I mean is the 2 (or more) planets would have to stay next to each other all the time, the same way moons do, but instead of one body revolving around the other like a moon does around a planet, the planets would both spin equally around each other, creating a single magnetic feild that could have as many moons as you wanted outside of the planets mutual revolution area. On a side-note, the tidal forces on those planets would be really strong, there would be crazy weather effects and stuff too.

That sounded complicated, I could draw you a picture that would be a much simpler explanation of the planets orbits and how it would all fit together. If you want a picture, IM me and Ill draw one with the IM doodler plugin.

Anyway, you could have three suns, with a gob of many planets circling each other and a hundred moons around them all. With the trillions of solar systems out there it wouldnt surprise me if there were a few like this already.

Answer 3

The differential equations of motion for the 'general case' 3-body problem are a real nightmare. In fact, they were only just 'solved' for the first time by a computer simulation about 40 years ago. But probably the only way that two planets could 'share' a moon would be for the planets to be orbiting each other around their common center of mass, and the moon orbiting at a much greater distance around the both of them. Trying for something like a 'figure 8' orbit around both planets would be tremendously unstable.

OTOH, as someone once observed, "The Universe is not only stranger than we imagine, it is probably stranger than we are 'capable' of imagining." (It sounds like something that Einstein might have said, but I don't remember for sure. This gettin' old sucks.)

HTH ☺

Doug

Answer 4

This could be possible! But the two planets should be, relative close to each other. Then the "system" could have a moon of its own. But because the two planets, probably rotate around the center of their system, the moon could probably have the problem that our moon has: It escapes gradually from our planet. In our moon this happens because of the seas we have. In the two system planets will happen because the rotation around the center of the "system" would have a similar effect. That means that if we find two planets with moons, this is a very early stage in that solar system.

Answer 5

It would not be possible. A planet's moon is held in orbit by the planets gravity. If two planets gravitational forces were acting on one moon the orbit would quickly become unstable and the moon would float off into space or crash into a planet. Not that the moon would ever be there in the first place.

Answer 6

It's not possible. The planets would have to be very close to each other and to the moon, and 2 planets are never so close. And the moon would not have an orbit because it would be caught in 2 gravity fields, which is also impossible.

Answer 7

It's possible - as long as the two planets *and* the extra moon orbited the same common center of gravity.

Alpha Centauri, Beta Centauri, and Proxima Centauri are the nearest stars to Earth, and it's actually a tri-nary star system. Alpha & Beta centauri orbit each other, and Proxima Centauri orbits *both* of those stars - but all 3 revolve around the common center of gravity.

Answer 8

Indeed, as others have explained above, it is possible....just very complicated. It's the same dynamic of planets orbiting a binary star...which most astronomers have every reason to consider as possible. However, the probability of this occuring is extremely low. But never say never...it's a big universe out there.

Answer 9

of course not