Planet Rotation: Questions & Answers

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Discussion Overview

The discussion revolves around the rotation of planets in relation to their stars, specifically addressing whether a planet's rotation direction aligns with that of its star, the reasons behind stellar rotation, and the variability of rotation among stars. The scope includes theoretical aspects of angular momentum conservation and observational characteristics of stellar behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that a planet's rotation around its star generally aligns with the star's rotation, attributing this to the conservation of angular momentum from the initial rotating cloud of dust and gas.
  • Others note that while this alignment is common, it is not a strict rule, citing exceptions such as Venus's retrograde rotation and the axial tilts of Uranus and Pluto.
  • There is a suggestion that all stars rotate, but the reasons for varying rotation speeds among them remain an active area of research, with some participants mentioning factors like magnetic braking during formation as a potential explanation for slower rotation in stars like the Sun.
  • One participant expresses uncertainty about the existence of non-rotating stars, prompting further inquiry into the topic.

Areas of Agreement / Disagreement

Participants generally agree that there is a correlation between the rotation of planets and their stars, but multiple competing views exist regarding the specifics of stellar rotation and the exceptions to the general rule. The discussion remains unresolved regarding the existence of non-rotating stars and the precise mechanisms influencing stellar rotation speeds.

Contextual Notes

Some statements rely on assumptions about the initial conditions of star and planet formation, and the discussion does not resolve the complexities of stellar rotation mechanisms or the potential existence of non-rotating stars.

Who May Find This Useful

Readers interested in astrophysics, planetary science, and the dynamics of celestial bodies may find this discussion relevant.

_DJ_british_?
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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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_DJ_british_? said:
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.

_DJ_british_? said:
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.

_DJ_british_? said:
And another question (well, two :P) : why do stars rotate (the outer layer, I mean)(And if it does, the inners?) ?
See above.
_DJ_british_? said:
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?
 
_DJ_british_? said:
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".
 
Just wanted to say thanks for ze info!
 

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