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Offline pete_inthehills

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planet orbit
« on: 11/09/2007 21:47:24 »
I was looking at a (not to scale) image of the planets orbit around the sun and I noticed that they all were more or less on the same plane.

Was this a trick of the image or do they all more or less orbit on a flat plane?

If so, why?


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Offline Mr Andrew

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planet orbit
« Reply #1 on: 11/09/2007 23:03:43 »
No, this is exactly the way it happens in reality.  The plane is called the ecliptic (I think).  Anyway, the planets are accumulations of rock or gas from the original debris cloud around the sun.  This cloud was spinning and so had angular momentum.  Since most of the particles in the cloud had to have the same angular momentum, when they coalesced, the resulting planets had that very same angular momentum (or close to it).
 

Offline DoctorBeaver

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planet orbit
« Reply #2 on: 11/09/2007 23:17:24 »
The plane is indeed called the ecliptic.

If I remember correctly, Pluto's orbit does not conform, which is 1 reason why some astronomers believe it was not formed from the cloud disk that formed the other planets.
 

Offline Soul Surfer

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planet orbit
« Reply #3 on: 11/09/2007 23:24:39 »
As a slowly rotating cloud is contracting to form a star and its associated planetary system the material initially spherical and having random motions forms into a disc This is because initially Coriolis forces push things very slightly towards the equator then the increasing mass creates gravitational attraction and finally any remaining material crossing the concentration in the disc tends to be deflected to join it.  It is from this disc that planets start to condense and eventually settle down into stable groups.  The further out you go in the solar system the less this effect applies so the Pluto asteroids have much more random orbits and can go well out if the ecliptic and comets which are the furthest out can come in from almost any direction.
« Last Edit: 11/09/2007 23:26:12 by Soul Surfer »
 

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planet orbit
« Reply #3 on: 11/09/2007 23:24:39 »

 

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