Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rotation of planets

  1. Oct 31, 2009 #1
    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!)?
  2. jcsd
  3. Oct 31, 2009 #2


    User Avatar
    Gold Member

    Generally, yes. But it is not a rule.

    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.

    See above.
    Don't know of any that don't. Do you?
  4. Nov 1, 2009 #3
    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.

    Yes. It's also hard to reverse direction when you're a planet.

    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".
  5. Nov 6, 2009 #4
    Just wanted to say thanks for ze info!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook