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Rotation of planets

by _DJ_british_?
Tags: planets, rotation
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_DJ_british_?
#1
Oct31-09, 09:29 PM
P: 42
I've read that a planet's rotation around it's star is in the same direction has the rotation of the star on itself, is that true? If so, why? Does it have something to do with the conservation of angular momentum?. And another question (well, two :P) : why do stars rotate (the outer layer, I mean)(And if it does, the inners?) ? And do all stars rotate? If not, why some do and some don't (four questions, I guess!)?
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DaveC426913
#2
Oct31-09, 10:36 PM
DaveC426913's Avatar
P: 15,319
Quote Quote by _DJ_british_? View Post
I've read that a planet's rotation around it's star is in the same direction has the rotation of the star on itself, is that true?
Generally, yes. But it is not a rule.

Quote Quote by _DJ_british_? View Post
If so, why? Does it have something to do with the conservation of angular momentum?.
Yes. The star and planets all condensed from the same cloud of dust and gas, and it is this cloud's initial rotation that is preserved.

Quote Quote by _DJ_british_? View Post
And another question (well, two :P) : why do stars rotate (the outer layer, I mean)(And if it does, the inners?) ?
See above.
Quote Quote by _DJ_british_? View Post
And do all stars rotate? If not, why some do and some don't (four questions, I guess!)?
Don't know of any that don't. Do you?
qraal
#3
Nov1-09, 06:39 PM
P: 775
Quote Quote by _DJ_british_? View Post
I've read that a planet's rotation around it's star is in the same direction has the rotation of the star on itself, is that true?
Kind of true. It's the direction the planets have as they orbit the Sun because they condensed from the same rotating mass as the Sun. Less true for rotation on their axes, as Venus rotates retrograde and Uranus and Pluto are tipped over.

If so, why? Does it have something to do with the conservation of angular momentum?
Yes. It's also hard to reverse direction when you're a planet.

And another question (well, two :P) : why do stars rotate (the outer layer, I mean)(And if it does, the inners?) ? And do all stars rotate? If not, why some do and some don't (four questions, I guess!)?
They all do, some much, much faster than others. It's an active field of research as to how they get fast or slow. The Sun's sluggish rotation is probably due to magnetic braking during its formation. Through interacting with the disk of ionized gas around it, the Sun lost rotational energy like a gigantic "disk brake".

_DJ_british_?
#4
Nov6-09, 07:52 PM
P: 42
Rotation of planets

Just wanted to say thanks for ze info!


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