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Thread: Does the Sun rotate?

  1. #1 Does the Sun rotate? 
    Forum Professor Daecon's Avatar
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    I don't believe I've ever heard a reference to how fast the Sun rotates on its axis, so I was wondering if it actually does rotate or not.


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  3. #2  
    Forum Cosmic Wizard
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    Yes and it was first noticed by observing the motion of sunspots.
    I don't remember the speed it rotates at any more. Somewhere around 27 days I think.


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  4. #3  
    Moderator Moderator Janus's Avatar
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    At the equator, the sun has a sidereal rotation of ~24.5 days,a and a synodic one of ~26.25 (sidereal is with respect to the stars and synodic is with respect to the Earth.)

    I specified the equator, because the Sun being a ball of gas, actually rotates at different speeds at different latitudes, with the slowest rotation at the poles.
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  5. #4  
    Forum Professor Daecon's Avatar
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    Oh thanks for that, I've never heard the terms sidereal and synodic before. (I know "synod" and the words seem to have a common root from the Greek word for "conjunction".)
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    Forum Professor astromark's Avatar
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    That 'Janus' has answered your question, I add a slightly complex view.. and Janus was not wrong. At the Observatory we use a sidereal time clock to time the motion of the drive motor.. It sits adjacent to a real-time digital clock.. We are often asked why they are not the same.. ( time ). With some arm waving and a little pointing to the large declination and inclination wheels of the Cook Telescope. 4 arc mins per day. ( sort of ) is the arrived at answer I use. That the motion of Earth on a curved path around Sol and that everything is actually moving. Sidereal time gives us a useful tool for accurate star finding. We do not all use the 'Go To' school of thought. That it's good to know why.
    One of the members has a Solar observing scope and we can actually see that in just a few hours the Sun spots have moved some.. interesting.
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  7. #6  
    Universal Mind John Galt's Avatar
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    An interesting point about the sun's rotation: although most of the mass of the solar system is in the sun, most of the angular momentum is in the planets. This observation has been central to deriving theories for planetary formation. In particular it requires some means of transferring angular momentum from the sun to the protoplanetary disc from which the planets form.
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  8. #7  
    Forum Radioactive Isotope cosmictraveler's Avatar
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    Watch here to see sun rotate.
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    not ADM!N grmpysmrf's Avatar
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    Why does it rotate? gravity?
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  10. #9  
    Forum Radioactive Isotope cosmictraveler's Avatar
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    Revolve means that one object circles another. The planets revolve around the sun and rotate on their own axis at the same time. The sun revolves around the center or our Galaxy and rotates around its own axis at the same time... taking the planets along with it in it's revolution around the greater gravity of the Galaxy center.


    All three events are caused by gravity. The differences are in where the center of gravity is . Rotation comes from a center of gravity within the objects own mass. Revolution comes from a (stronger) center in another (usually larger, although not neccessarily , as is the case with a black hole)
    mass.


    Or, as is the case of binary stars that revolve around a shared center of gravity outside of both objects.
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  11. #10  
    Forum Professor astromark's Avatar
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    ~ Angular momentum of the condensing field of planetary nebulous mater. = spin = rotation.
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  12. #11  
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    Quote Originally Posted by grmpysmrf View Post
    Why does it rotate? gravity?
    There was rotation, compared to the interstellar medium (i.e. the galaxy), in the primordial gas and dust cloud from which the Solar Nebula formed.

    Remember that from the point of view of a fixed spot with a gravitational attraction, motion off center from that spot will result in rotation. To put it another way you can make a small playground merry-go-round spin by pushing forward on one side.

    It is so with solar nebulae, too.

    And +1 for a good question.

    And a +1 for a good one in the IP too.
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  13. #12  
    Forum Professor pyoko's Avatar
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    Giant sunspot makes third trip across the sun

    a magnetically strong and complex region on the sun's surface – has just appeared over the sun's horizon. This is the third trip for this region across the face of the sun, which takes approximately 27 days to make a complete rotation.
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