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behavioralist

Ring-inclination, axial and moon drift.

6 posts in this topic

1. Is ring-development confined to the equatorial plane; Zero-inclination?

Do rings remain on the equatorial plane if they developed there, when the planet's axis drifts?

Does ring development tend to extend farther from the planet than just those rings or ring-segments which are compelled to follow the axial drift?

---so that if the axis of a planet with rings has drifted it will have left a trace of where it was when the rings developed?

2. Let's say that a planet has been drifting on its axis, and the rings are extending as far as plausibility permits them to be constrained by the attraction of the equatorial plane; but we find no sign beyond that outer edge to indicate the original position of the rings at formation. Then, what forces might have "blown away" these signs?

3. Saturn: one, or possibly two moons, manifestly having been caught inside the rings for a time. (If we don't want to indulge in the popularized notion that the equatorial plane forces of minor moons can support rings.) How considerable a time?

Saturn drifted, as I judge by the inclination of the outer ring per above. And the orbital changes of some of its moons clearly were not the result of only that drift, which perhaps was quite steady and is still going on. There's a math begging to be developed there!

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First up, this topic is not well understood - science has a long way to go to fully understand orbital mechanics at this level...

1. Is ring-development confined to the equatorial plane; Zero-inclination?

Not exactly, but the most efficient energy configuration is for equatorial, so if any developing ring had any slight imbalance either above or below (and of course it will..), it will tend to wobble itself into the equatorial plane, given a long enough period of time.

Do rings remain on the equatorial plane if they developed there, when the planet's axis drifts?

Surely their paths are mostly dependent on the centre of gravity, so minor axial drifts will have little or no effect. To be tilted dramatically, eg Uranus, something has to happen, eg a close encounter or collision.. Here's an interesting link..

Does ring development tend to extend farther from the planet than just those rings or ring-segments which are compelled to follow the axial drift?

As above, I don't think they do follow any axial 'drift'. My understanding is that in the case of Uranus, the rings developed (or re-developed) at the time of the collision/encounter, not when the planet was formed, hence their orientation - the whole Uranus system is often referred to as an unstable configuration (although an unusual alignment of moons might keep the rings and axial rotation where they are..). It is expected that they will eventually re-align to the solar system's plane, but like I said above, the physics is complex and difficult to predict.

---so that if the axis of a planet with rings has drifted it will have left a trace of where it was when the rings developed?

Don't know, but sounds very unlikely to me, for reasons that are sort of outlined above..

2. Let's say that a planet has been drifting on its axis, and the rings are extending as far as plausibility permits them to be constrained by the attraction of the equatorial plane; but we find no sign beyond that outer edge to indicate the original position of the rings at formation. Then, what forces might have "blown away" these signs?

No idea, but you seem to be building a case on something that wasn't correct from the start.

3. Saturn: one, or possibly two moons, manifestly having been caught inside the rings for a time. (If we don't want to indulge in the popularized notion that the equatorial plane forces of minor moons can support rings.) How considerable a time?

Well, since they were formed.. :D But why do you not want to 'indulge' that moons affect ring formation? They DO. Every bit of mass around the planet is significant, larger bits are *more* significant.

Since you now move even further, based on dismissing other science, I'll leave it there.

Edited by Chrlzs

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behavioralist, how do you explain the extra 'gravity kick' that shepherding moons seem to exert in Saturn's ring formation?

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The apoapsis of the 2 most eccentric rings (a and b, to keep from having to pull up the character tray) sort of excuses them for their non-negligible inclination. Odd to me, with no realistic model to look at (and how big it would have to be to show the ring inclinations adequately!), is that the innermost rings of uranus have the greatest inclination. That, to my stubborn notion of rings, must be accounted for by some atmospheric condition on u, or an external-to-u gravitational force.

But as a rule uranus follows the code: negligible inclination. So my question still stands: is there an outermost remant of where the disc formed?

And it invites to me the question: what forces besides the mass per area (no torus) of an accretion disc can make one actually solid as rock? How much force can an equator wield? That question ought to be susceptible to observation, since the force must abate with orbital distance.

Also, perhaps because I'm naive enough to stick with an old notion of mine that uranus is just the disconnected atmosphere of a planet serving as a core aqligned with the magnetic poles, I wonder if isn't a possibility that the planet actually ate a considerable moon? ---that would be quite a disturbing process! ---and there is evidence of argument between moons.

Edited by behavioralist

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behavioralist, how do you explain the extra 'gravity kick' that shepherding moons seem to exert in Saturn's ring formation?

Interesting link. The planet-side ring naturally tries to expand in the absence of pan, as the other side is far less inclined to do, and pan redirects that expansion energy (except as mass falling onto pan) like a sheepdog,

peak events presumably in a predictable pattern of time-intervals though not likely to occur at the same places on the ring,

(not much indication at that page of the shape of the rings and of the pan orbit; we see pan in the middle of the gap, which presumably isn't consistent with the phenomenon; nor of how the gap/ring breadths fluctuate, the ring's tides)

so that each peak of incidence is rather unprecendented where it happens, and perhaps each usually happens where previous pressures have subsided or exhausted the energy,

possibly everything has subsided locally before every next peak of pan's brushes with the ring incidents.

Otherwise we have, as the most interesting predictable feature, the remaining uncommon peaks where a new peak excites an area where there is still a sign of a previous activity.

Edited by behavioralist

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behavioralist, how do you explain the extra 'gravity kick' that shepherding moons seem to exert in Saturn's ring formation?

Also there is pan's tidal pull, compounding the centrifugal expansion of the ring and any possible shape-difference between pan's orbit and the shape of the edge it's trimming, and the velocity of the marvelous orbiting saucer pan relative to the ring, to consider. Plus how pan's diameter has grown. Perhaps there is even some unique harmonic between the rotation and equator-velocity of pan and the relative velocity of the orbit.

The centrifugal expansion is the effect of the moon's trimming. The moon has forced back some expansion that would be natural to an unshepherded ring. Some of that mass collects on the moon, but most is pushed back to where it wants to expand again. Hence the ripples, expansion in flux. An interesting idea to calculate when the moon will have eaten all of that; maybe then, no more ripples.

I haven't looked for pan (I never saw it as a bit unique before) at any other pages but the one you linked to, yet, but I observe, at second glance, that you mention this effect at more than one of satrun's moons; but you din't link up to more than one.

Edited by behavioralist

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