So from what i’ve read, Jupiter’s moons ( Europa, Ganymede, Io) are basically squeezed, stretched and pulled in different directions by Jupiter’s gravity, and more or less by themselves.
How do they remain in a stable orbit ?
Do these gravitational forces cancel eachother out, thus creating a perfect stable orbit ?
In: Planetary Science
In the case of a single moon orbiting a planet, it doesn’t really matter how big the planet is, there are stable orbits. As long as the moon doesn’t get too close that it gets pulled apart (called the Roche Limit) or too far away and it just flys off into space.
Between those two extremes is a place where things can orbit. Jupiter has a lot of stuff orbiting in this space.
But the moons also pull on each other. Wouldn’t that make the orbits unstable?
Well yes this can happen and results in moons being flung too close to the planet or ejected from the system completely. There are gaps around Saturn where nothing has a stable orbit because of the interactions between moons, which is why there are gaps in the rings.
But an equilibrium can reached where the moons close to each other fall into what is called orbital resonance.
So take the 3 inner moons of Jupiter. Io, Europa, Ganymede. For every orbit that Ganymede does, Europa does 2. For every orbit Europa does, Io does 2. So Io completes 4 orbits for every one of Ganymede’s.
This has the effect of correcting each moon’s pull on the others so that none of them lose or gain momentum from the interaction. This makes their orbits stable.
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