General Question

Qingu's avatar

If a planet migrates into a new orbit, what exactly happens to its satellites?

Asked by Qingu (21070 points ) January 23rd, 2011

We know that planets have migrated their orbits in the past. There’s evidence that the outer gas giants’ orbits have changed in our solar system—and in other star systems we’ve found many Jupiter-sized planets that have probably migrated very close to their sun.

But if a planet’s orbit changes and it has satellites, what happens to their orbits? Do they change at all? To what extent would it depend on the nature of the force that changes the planet’s orbit?

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11 Answers

Rarebear's avatar

The satellites would probably follow the planet unless there is another stronger gravitational force to pull them away.

filmfann's avatar

@Rarebear is correct, and about 30 seconds faster than I am tonight.

ETpro's avatar

Generally, @Rarebear & @filmfann would be correct. But yes, @Qingu, your hunch that it would depend on what caused the orbital variance is correct as well. Unstable orbits vary rapidly till they reach a point of stability or the orbiting object is consumed by the gravitational pull of the object it orbits. It’s anybody’s guess what happens to satellites of the object if its orbit is highly unstable. Objects in stable orbits very gradually lose orbital speed. The few hydrogen atoms in space give some resistance, and solar winds add to that, making an apparent headwind the object must move through. Slowing of orbital speed tends to cause the object to spiral closer to the body it orbits. Counterbalancing this, the Sun and other stars lose mass as they convert their fuel into energy. This loss of mass tends to cause objects orbiting them to move further away.

As planets with satellites draw ever closer to a very massive object like a star, the orbit/s of their satellite/s become progressively more disturbed by the massive object’s gravity. Moving further away tends to lessen this effect.

Finally, orbiting planets can have their orbits affected by collisions with large objects. Any collision sufficient to produce a major alteration in the orbit of the planet might have a profound influence on satellite orbits as well.

So the answer truly is, it depends.

Vortico's avatar

You might be able to set something up on PhET’s My Solar System and see for yourself.

koanhead's avatar

@Vortico
Thanks for the awesome link! Now I’m going to be up all night playing with this thing :^)

CaptainHarley's avatar

Yeah. Thanks a lot for that link, @Vortico . My wife is already fussin’ at me about it! LOL!

PhiNotPi's avatar

The satellites would follow the planet. Since orbit migration is a continous process, the planets may still be migrating today. Yet, as you can see, the satellites orbiiting them are still doing so.

mattbrowne's avatar

Wow. Great question. Well, it might actually be a bit trickier than satellites merely following their planet. As a thought experiment, suppose some cosmic magician is playing pool hitting Earth hard with her cue stick. What really happens to our Moon depends on the acceleration and the new velocity and direction of Earth compare to the velocity of the Moon. If the difference is huge, the satellite might actually not be able to follow. I’d have to think about the math behind this. Perhaps we can calculate the threshold.

the100thmonkey's avatar

The orbits of the moons will change, even if beyond our ability to meaure them – they too will be affected by the gravitation(s) of the body/bodies that disrupt(s) the stability of the parent planet’s orbit.

Whether or not the new system is stable is where it gets fun!

Sarah90's avatar

@Rarebear
Would Kim Kardashian’s big butt qualify ??

SecondHandStoke's avatar

^“I like big buts and I cannot lie.”

Well, most…

….......

Actually yes.

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