# Why do planets orbit in approximately the same plane as other planets?

Discussion in 'Highly Technical' started by Apple Of Sodom, Feb 7, 2013.

1. ### Apple Of Sodom Golden Member

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Maybe I'm just not thinking of this properly...

Why do all of the planets in our system orbit the sun in approximately the same plane? Do other systems exist that have planets orbit a star orthogonally (or at least significantly different angle) from one another? Is this even a possibility? Is there basically a plane that has the strongest gravity so all stellar objects in orbit will eventually find that plane, like an equilibrium?

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3. ### mryellow Junior Member

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I believe the accretion discs form along the plane of the stars rotation because of gravity.

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4. ### Vectronic Senior member

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It's possible to have all sorts of weird orbits going on at the same time, take a look at Jupiters moons.

The initial accretion disc inevitably has to follow the spin of it's largest/central mass... thus if enough material is there to eventually form a planet(s), it will be orbiting in that plane. A planet that forms out of that plane (which wouldn't form a planet at all really, maybe a small clump), doesn't have the momentum to maintain an orbit, so it either:
A. falls into the center of gravity.
B. flies off, if given enough time and depending on the rotation of the center of gravity, it may be able to "hang on" to an orbit really far away that matches the gravitational pull and it's momentum.

Planets/bodies that are "close" to the orbital plane, will eventually alter their orbit, or alter the plane so that they are both in-line... or... failing that, fly off.

Something like Pluto will probably eventually match the orbit of the other planets, because of the pull/gravity between it, and the much larger planets... since Pluto is so small this may take billions of years... in the meantime it's more likely to bump into something else and become an unstable orbit... dive in, or fly out.

You can play with stuff like this with something like Universe Sandbox... not terribly accurate, but accurate enough.

Disclaimer: I dunno s**t.

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5. ### Biftheunderstudy Senior member

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The best model for solar system formation is the planetary disk. So why a disk?

If you start with a big cloud of gas with some net sense of rotation (the reasons to believe these initial conditions aren't that far fetched). As gravity collapses the cloud, it will collapse along the z axis preferentially since there is no rotational support there. (Rotational support being the angular moment or centrifigul force). So, if you take a rotating sphere and collapse it, it will invariably produce a disk like structure where the planets will form in.

Now, this is only part of the answer, the rest has to do with where the stable orbits are (resonances etc.)

If you look at the larger scale of the solar system (Kuiper belt and Oort cloud), this co-planar nature is basically completely lost (Pluto being a fine example of this type of orbit).

If you look at other gravitating systems like star clusters, galaxies, galaxy clusters etc. there is no constraint on their orbits being co-planar, in which case the velocity distribution is said to be isotropic.

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6. ### disappoint Lifer

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I always thought it was because of spin.

Think of a weight at the end of a string. This weight has some other weights glued to it. Take the other end of the string and spin it fast enough to overcome the glue. Would the weights that detach not be likely to fly off in the plane that you spun it?

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7. ### Ferzerp Diamond Member

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The items that orbit in the plane are items that formed from the spinning cloud of matter.

Items that are orbiting not with that plane are captured items.

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8. ### LightField Member

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Do a search for a video made by someone called Stan Deyo... he sounds like a conman but from what I have discovered there may be some truth to his claims.

I might be just ignorant or delusional but from what I have seen rotation has something to do with gravity.... as does electricity and magnetism.

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9. ### John Connor Lifer

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Another question is why do most celestial objects rotate in a counter-clockwise direction?

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10. ### crashtech Diamond Member

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Perceived direction of rotation is dependent on orientation, counterclockwise rotation from one side appears clockwise from the other.

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11. ### wirednuts Diamond Member

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is this the answer? it makes sense

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12. ### John Connor Lifer

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I just envisoed Jupiter turning counter-clockwise and it doesn't matter which side you see the planet it moves counter-clockwise. Same with galaxies.

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13. ### OSULugan Senior member

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Think about looking "down" onto the axis of rotation from the "top" of a planet.

Now, think about looking "up" onto the axis of rotation from the "bottom" of the planet.

If you need to, use your hand.

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14. ### John Connor Lifer

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And another question. What if instead of traveling out into space you travel down or straight up? What's up or down? I wondered about that since I was about 9 years old.

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15. ### wirednuts Diamond Member

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sort of what were talking about. not really an up or down, but there is up and down. the universe started at the size of a head of a pin or less. then it exploded in flat ring like fashion. the universe is flat. space goes on forever, as far as we can tell, but the universe is basically a big flat disc.

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16. ### John Connor Lifer

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We think it's flat. They said earth was flat at one time too. I think it's a big ass sphere.

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17. ### Sunny129 Diamond Member

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while spacetime can have significant curvature locally (meaning near relativistic objects such as black holes, neutron stars, galaxy clusters, etc.), the universe on a grand scale appears to be flat. but don't let the terminology confuse you - stating that the universe is "flat" simply means that spacetime is not curved. it does not mean that the universe expanded from the Big Bang in 2-dimensional fashion. we live in a universe of 3 spatial dimensions, and space has been expanding into all 3 of those spatial dimensions from the onset. that is to say, the universe is expanding like a beach ball being blown up, and not like a "flat disc" of ever-increasing radius.

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19. ### piasabird Lifer

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What makes you think this actually occurs? We have not studies many solarsystems. However, if you look at most galaxies they tend to radiate out from an axis like a wheel. This may have something to do with magnetic patterns of rotational systems. So maybe a planetary system works much the same.

Then you look at formations like Pilades which is a star cluster and you wonder what is keeping it together.

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Last edited: Feb 22, 2013
20. ### piasabird Lifer

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Using the hubble telescope, the further away the objects the less linear they seem to be. So maybe as stars evolved and collapsed they developed into linerar structures. This assumes that the further away something is the longer the light takes to reach Earth so it is like looking back in time.

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21. ### Comdrpopnfresh Golden Member

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omfsm! I've oft wondered the same thing. My best guess is that because solar systems form in a galactic orbit they are prone to formation from clouds that compress along a common plane aligned to galactic center. The thing that always brought me to this same question is reflection on our own asteroid belt: is it a spherical formation? does our NEO search include object with approach paths bringing them toward our poles? why do we launch all our ranged satellites (think voyager(s)) on a planetary plane only? Good to know I am not the only one wondering this. (apologizes for not taking the time to read any responses past the first 1-3... forums need to adopt a rating system like Amazon product comments; "xx other users found this useful/ made a similar comment").

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22. ### Sunny129 Diamond Member

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ranged satellites need to reach high velocities in order to escape the sun's gravity and get to the outer reaches of the solar system (and perhaps beyond, like the Voyagers might soon be). scientists deliberately launch these satellites in such a way that they make "near passes" by another planet (or planets), thereby using that planet's gravity to accelerate and slingshot themselves away from the sun and farther out into the solar system (think back to Kepler's 2nd law of planetary motion, which implies that in an eccentric (elliptical) orbit, the object must move faster when it is closer to the source of gravitation). to reach the highest velocities possible in this manner, these satellites must travel in the direction of the planets' orbits around the sun, and they must stay within the plane of the ecliptic (the orbital plane of the planets).

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Last edited: Feb 22, 2013
23. ### Ventanni Golden Member

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Pluto orbits in a 2:3 resonance with Neptune

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24. ### Sunny129 Diamond Member

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while true, this phenomenon doesn't really answer the OP's question of why the planets tend to orbit in the same plane.

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