What causes orbits to be inclined?

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Summary:

Or what are the characteristics that generally predict inclined orbits?
I want to know what are generally the characteristics that can predict or things that could cause the orbit of an object to deviate from zero degrees relative to the equatorial plane of the object that it is orbiting?
 

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  • #2
russ_watters
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To start with, at the time the solar system is formed, it is one cloud with a net rotational momentum and for a few reasons tends to coalesce into a disc. So that's the starting point of your expectation. But nothing is perfect, and the planets interact most notably with each other, which causes them to move from perfect alignment. But not much; all of the [currently defined] planets are within single digit inclinations of each other.
 
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  • #3
Keith_McClary
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single digit inclinations
I guess you mean single digits of degrees (from the ecliptic plane?).
 
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russ_watters
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I guess you mean single digits of degrees (from the ecliptic plane?).
Yep, skipped a key word.
 
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DaveC426913
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...deviate from zero degrees relative to the equatorial plane of the object that it is orbiting?
So, to tease this apart a little:

Are you thinking about how planets might have aligned in the plane of their parent star? Or are you thinking more about how moons might have aligned in the rotational planes of their parent planet? (not to mention comets and asteroids).

Because I think there's some nuances in how the initial conditions evolve to the observed conditions.

Example:
Planets evolve from a vaguely spherical, rotating gaseous cloud of a proto-solar system on a broadly similar timeline as the sun itself coalesces.

But moons are not necessarily analogous - they do not likewise evolve from a vaguely rotating spherical gaseous cloud of a proto-planetoid, coalescing at the same time.

There's a lot of moons that get their orbits long after their parent planets have coalesced. Some captures, some impact ejections, etc. These have no analogue for planets.

Apples and oranges, you see.
 
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sophiecentaur
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The original nebula, assuming it contains all the material of a future solar system, will be very much three dimensional. It will have a certain net angular momentum., which will remain constant. There will be an axis for this angular momentum. As gravity draws the material together, momentum will always be conserved but the kinetic energy won't be. That will cause objects to form and grow. The central star will get most of the material but there will also be planets and dust clouds. the mass will be near a single plane but only near. Any collisions can have the effect of knocking the objects out of the plane. The present arrangement of the solar system is fairly stable (in our time scale) but, if two large planets were to collide, the results could be way outside the plane of the ecliptic. This would require more than just the two colliding planets.
 

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