I understand there’s quite a few forces that prompt the disk shape of rings: particles in toroidal orbits interacting and cancelling their momentums; magnetic field lines being weakest farthest from the poles; corriolis effect drawing particles towards the path of least rotation; etc…
By why specifically the equator? Why don’t rings align with the poles, or some other angle? And why is this also the case for black hole accretion disks?
In: Physics
Rings are usually made out of moons that got too close, so rings are usually in same inclination as the moons of a planet.
The question then becomes; why do moons usually have very low inclinations?
If the moons formed with the planet out of the same disk of dust and debris, then they will all have had the same spin and end up in the same plane with very little inclination relative to the planet’s equator.
If the moon formed from an impact with the planet (as our moon probably did) then that impact will have aligned the rotation of the planet with the forming moon.
However if the moon was captured, all bets are off. Triton is inclined by 156 degrees relative to the equator of Neptune.
Theoretically a captured moon could decay below the roche limit and become a heavily inclined ring.
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