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Plausible?

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Thu, 2013-01-03 14:01

#1

Prophet710 Prophet710's picture

Prophet710's picture

Plausible?

http://knucklehead2079.deviantart.com/art/Outer-Reaches-346483280 The planet has a moon and the moon has its' own satellite. Even plausible considering hard physics? Am I missing something or is this just a cool picture?

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"And yet, across the gulf of space, minds immeasurably superior to ours regarded this Earth with envious eyes. And slowly, and surely, they drew their plans against us."

Thu, 2013-01-03 17:48

#2

bibliophile20 bibliophile20's picture

bibliophile20's picture

So long as the satellite's

So long as the satellite's satellite (sub-sat?) is within the satellite's Hill Sphere and outside the Roche Limit, it's plausible. But unless the picture is messing with scale (the satellite and sub-sat being actually pretty far away from the main planet) that picture is not possible. But, as a general rule, it is certainly possible for an object orbiting another body to have its own satellites--after all, of the planets and dwarf planets and even asteroids in this system, we know of dozens if not hundreds of moons, and all of their parent bodies orbit the Sun. (Also, NASA is making noises about plans to capture an asteroid and put it in orbit around Luna; I'll believe it when I see it). EDIT: And as for that picture, here's a perspective shift to consider: of the three bodies, from farground to foreground, there's a blue, a gray and a red/orange. Instead of the Red-Orange body being the parent, take a look at that picture with the following thought in mind: the blue body is the parent body, and both the gray and red/orange bodies are orbiting it. The blue body is just really far away.

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"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

Thu, 2013-01-03 19:43

#3

Undocking

Undocking's picture

Depending on the size of the

Depending on the size of the moon and the distance from the planet, a moon could have its own moon. As bibliophile pointed out, the setup in that artwork would not be probable. Exomoons with "moonlets" orbiting them would generally be short-lived because the planet would pull the moonlets away from their moons. However, if the distance was far enough between the moon and planet and the moon was large enough, then it could work out. Edit: What else would be cool is having a binary planet system (like Charon and Pluto) on a larger scale. Charon and Pluto do have a few moons (Nix, Hydra, and the two S's). If bibliophile's edit is how you want to view it, then red and blue could be binary.

Sun, 2013-01-06 05:08

#4

Arenamontanus Arenamontanus's picture

Arenamontanus's picture

Agree with the above.

Agree with the above. Generally moons with moons are rare, since the Hill and Roche sphere can be fairly close to each other. But Rhea may have rings, http://en.wikipedia.org/wiki/Rings_of_Rhea , and hence plenty of tiny moonlets. Of course, saying that X orbits Y can be mildly tricky. For example, the Saturn moon Dione has Helene (formerly Dione B) in the leading Lagrange point and Polydeuces in the trailing one. So in one sense the two smaller moons are fixed relative to Dione (as seen from its surface), in another sense they orbit it once per revolution (as seen from an outside view).

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Sat, 2013-01-12 11:00

#5

Lorsa

Lorsa's picture

Another thing to consider

Another thing to consider would be to have two moons of identical size orbiting their center of mass which is in turn orbiting the planet. It would be sort of a twin-moon configuration which would be possible in theory.

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Sat, 2013-01-12 11:26

#6

Arenamontanus Arenamontanus's picture

Arenamontanus's picture

Lorsa wrote:Another thing to

Lorsa wrote:
Another thing to consider would be to have two moons of identical size orbiting their center of mass which is in turn orbiting the planet. It would be sort of a twin-moon configuration which would be possible in theory.

Good idea! Rocheworlds are always fun. There will be a complicated interplay of tides affecting the dual moons, increasing and decreasing their separation in certain patterns. I suspect this will produce some equally impressive volcanism and surface processes, as they adjust their shape.

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