Solving Orbital Plane Alignment of Two Planets

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Discussion Overview

The discussion revolves around the orbital plane alignment of two planets orbiting the Sun, considering their interactions with each other and with the Sun. Participants explore the dynamics of their orbits and the conditions under which alignment might occur, delving into theoretical implications and physical intuition.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant proposes that the orbital planes of two planets will eventually align due to their interactions, likening the system to a damped harmonic oscillator.
  • Another participant questions the premise of alignment, asking for clarification on the source of damping in the system.
  • A different viewpoint suggests that the potential energy between the two planets reaches a minimum when they are aligned, rather than relying on damping forces.
  • One participant argues that while the nodes of their orbits may precess, the planets will not become co-planar without additional forces acting on them, citing the time-reversibility of point mass n-body problems.
  • This participant also references the co-planarity observed in various celestial systems, attributing it to specific forces, such as tidal effects, but notes that these forces may not apply to the planets in question due to their distance from the Sun.

Areas of Agreement / Disagreement

Participants express differing views on whether the orbital planes will align, with some supporting the idea and others challenging it. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Participants acknowledge the complexity of the interactions involved and the potential influence of additional forces, but do not reach a consensus on the mechanisms that would lead to alignment.

chronnox
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Im trying to solve (approximately) the following problem: Suppose that i have 2 planets with mass m1 and m2 orbiting around the sun and i take into account the following interactions:
a) Interaction between planet 1 and the sun
b) Interaction between planet 2 and the sun
c) Interaction between planet 1 and planet 2

Where the sun has mas M >> m1,m2 . My physical intuition tells me that this system is similar to a damped harmonical oscillator so at later times the orbital planes of the planets will be aligned, i.e., the angle between the orbital planes will be zero at later times. The problem is that i can't find a book or an article which can help me with this. Does anyone know a good book to start with? or a book with a method to solve this problem?. Finally do you agree with my proposal that the angle between the orbital planes will be zero at later times?.
 
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i'm not so sure the alignment will happen. Where does the damping come from?
 
It's nice idea. It is not the damping force, i think just potential energy between the 2 planets will get the lowest value when they are aligned.
 
Assuming that their orbits are far enough apart that their orbits are stable, their nodes will precess, but they will never become co-planar unless some other force is at work.

One way to think about it is that point mass n-body problems are time reversable. So if they did become co-planar, it would imply that a perfectly co-planar system could also break free of its co-planar state.

We observe a lot of systems that are roughly co-planar in our solar system. The planets around the Sun all orbit within < 20 degrees. The inner moons of Jupiter, Saturn, Uranus, and Neptune are roughly co-planar, but they probably formed that way.

Mars has two moons that are roughly co-planar even though they may be captured asteroids. This does imply that there are forces that will make objects co-planar. In this case, I believe it is the tides they raise on Mars, and Mars's equatorial buldge that makes their orbits settle into equatorial orbits. So the moons didn't do it to each other. Mars' non-spherical shape caused them to both become equatorial orbiters.

But the Sun takes 30 days to spin once. It has practically no equatorial buldge. And even if it did, the planets are sufficiently far from the Sun that it could be accurately approximated as a point mass, and the planets would never feel a significant pull from this buldge. Additionally, the planets are too far to pull a significant tide on the surface of the Sun.
 

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