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Our solar system

  1. Apr 15, 2006 #1


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    I had a thought about the possition of the sun in our SS, and wondered if
    the suns possition varied by any significant amout due to the gravitational
    pull of the planets, all the simulations i can find have the sun static.
  2. jcsd
  3. Apr 15, 2006 #2


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    The Sun orbits around the Centre of Mass of the Solar system, just as all the planets do.

    However, in the two body Newtonian problem you can transform the orbital motion around the CoM into an orbital motion, to a non-inertial frame of reference, around either of the masses. Normally the Sun is taken as the origin of the coordinate system, and the planet performs a Keplerian ellipse around it.

    Last edited: Apr 15, 2006
  4. Apr 15, 2006 #3


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    Hi Garth, i imagine the center of mass is not far from the sun, so the sun would wobble , rather than actually orbit, but is this a chaotic wobble, due
    to having so many planets to pull on it. or is it more than a wobble.
  5. Apr 15, 2006 #4
    Wolram, your imagination is abseloutely correct and its just a wobble and not more.
  6. Apr 15, 2006 #5


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    With the Sun being 99.8% of the mass of the entire solar system and Jupiter being most of the rest, the center of mass would be very near the core and well below the photosphere, It might even be in the core (however defined) and the wobble would be very small. Even that small wobble effected by Jupiter would often be offset some by any other solar system masses opposite Jupiter at the time and I don't know if the wobble would even be detectable...:confused:
  7. Apr 15, 2006 #6


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    The wobble of stars is one of the main tools used in detecting extra solar planets. This can be done by astrometry (carefully measuring the position of a star over a long period of time) or by doppler shifting of the stars spectra. I did see a website a while back that demonstrated the suns wobble with a video and it is rather erratic and mainly due to Jupiter. I can't find it at the minute but if i do I'll post it.
  8. Apr 15, 2006 #7


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    I was going to mention that (extra solar planets) but I think I remember that most found by this method are much larger than Jupiter and quite a few are much closer to thier primary than Jupiter is to the Sun.

    But, a quick search shows me that I was wrong and that the barycenter of the Earth-Jupiter system is a bit outside the Sun's photosphere as described by the heretical "Wikepedia" source:
    and more, including the animations, at:
    and more stuff at:

    Guess I better stick to stellar stuff and leave the solar system stuff to Janus..:cry:
    Last edited: Apr 15, 2006
  9. Apr 15, 2006 #8


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    Last edited: Apr 15, 2006
  10. Apr 15, 2006 #9


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    The solar system barycenter is often outside the photosphere of the Sun, but not outside the corona.

    Here is an image of the Sun locked to the center of the screen:

    Unlocking the Sun exposes the solar system barycenter which is now locked to the center of the screen. The Sun spends nearly a decade in this image circling the solar system barycenter:

    Editing the Sun and setting its size to 0 while retaining its mass allows me to zoom in on the solar system barycenter and observe the Sun's path around it:

    The center of the Sun strays near its maximum barycenter distance of about 1.3 million kilometers on Dec. 3, 2022.This can be corroborated by querying the JPL Ephemeris system which gives the following data for Dec. 3, 2022.
    2459916.500000000 = A.D. 2022-Dec-03 00:00:00.0000 (CT)
    1.357796530286104E+06 -5.340761458326381E+04 -3.117957726829686E+04
    -9.802716335062548E-04 1.565705785929941E-02 -1.077297045285839E-04
    4.533817068543462E+00 1.359204163100999E+06 -1.592002604514373E-03

    The boldfaced, italicized number represents the Sun / solar system barycenter distance (km) on that date.

    In the simulation, editing Jupiter, and setting its mass to 0 demonstrates that Jupiter is responsible for the majority of wobble.

    Saturn is the next strongest perturber. Additionally, setting its mass to 0 shows:

    The next strongest perturber is Neptune. Additionally, setting its mass to 0 causes the Sun's motion around the solar system barycenter to trace a circle around its barycenter. Uranus is responsible for this circle. The Sun's period around the barycenter and Uranus' period around the barycenter match.

    Zooming in exposes the effects of the smaller planets on the Uranus-induced circle.

    Setting Uranus' mass to 0 eliminates the Uranus-induced wobble. The Sun's center now appears to rest on the solar system barycenter.

    But zooming in further exposes the influences of the remaining planets on the solar system barycenter: The Earth/Moon system is responsible for the majority of the wobble

    Setting the Earth/Moon mass to 0 leaves Venus as the most significant perturber. It has the following influence:

    Setting Venus' mass to 0 leaves Mercury, Mars, and Pluto as the sole perturbers. They cause the center of the Sun to trace the following path around the solar system barycenter:

    Zooming in for a clearer view, the effects of Mercury and Mars are seen. Pluto's effects is simply pulling this pattern off-center. If left to run for a quarter century of sim time, the entire pattern would trace a circle around the center of the screen:

    Setting Mars, which is now the most significant perturber, to 0 shows Mercury's influence causing the center of the Sun to trace circles around the solar system barycenter:

    Letting this simulation run for half of a Pluto orbit exposes Pluto's influence on the solar system barycenter.
  11. Apr 15, 2006 #10


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    Thankyou everyone, the links you provided etc have been most interesting,
    i imagine the seasoned space pilot would have to know his orbits. :biggrin:
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