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The suns gravitational effect

  1. Nov 19, 2008 #1
    Is the suns gravitational effect different on various parts of the sun? Is it stronger at the equator of the sun that it would be at the north or south poll? I did a search for this online and on here but did not find anything, so any help would be very much appreciated.
  2. jcsd
  3. Nov 19, 2008 #2
    The Sun turns on its axis much like the Earth does. This motion creates a sort of cetripetal counter force to the gravity of its mass. So like a spinning top, something at the poles would receive the full effect of the Sun’s gravity, whereas something at the equator would get a slight boost from the spin. The ESA uses this effect when space missions are launched from French Guiana near the Earth’s equator. Some huge stars actually bulge visibly at their equator.
    If this is what you had in mind.
    Last edited: Nov 19, 2008
  4. Nov 19, 2008 #3
    Yes thank you very much.
  5. Nov 19, 2008 #4
    No problem, and welcome to the forum!
  6. Nov 19, 2008 #5


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    I interpreted this a little differently: "would an object in space, NOT on the sun, NOT rotating with it, such that a straight line from the center of sun to the object passes through a pole, have different gravitational force on it than an object in space such that a line from the center of the sun to the object passes through the equator of the sun?"

    Since the rotating sun is be an "oblate" spheroid, wider at the equator than at the poles, there is more mass pulling on the object directly above the equator than on the object directly above the poles. The gravitational force will be greater on an object directly above the equator than on an object directly above the poles.
  7. Nov 19, 2008 #6

    That makes sense, I looked into oblate spheroid's and found some good information about the effect of gravity at or around the equator vs the poles.
  8. Nov 19, 2008 #7

    D H

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    The effect is very, very small for a couple of reasons. Firstly, the influence of any gravitational body's quadrupole moment decreases as the inverse fourth power of the distance from the object. Secondly, the Sun's gravitational quadrupole moment (solar J2=10-7; c.f. Earth J2=0.00108) is very, very small because the Sun is very close to a perfect sphere (solar flatening=9×10-6); c.f. Earth flatening=0.0034). The end result is an extremely small effect. Think of it this way: The effect of the Sun's oblateness on Mercury's orbit is much, much smaller than the relativistic precession.
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