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Wm. R. Ward, R. M. Canup (Southwest Research Institute, 1050 Walnut St., Suite 400, Boulder, CO 80302)
The spin axis precession rate of Jupiter is very close to the nu17 secular frequency of the solar system, which is the principal term describing the ~ 4.3 x 105 year regression of the Uranus orbit plane. This is reminiscent of the proximity of Saturn's spin axis precession rate to the nu18 that describes Neptune's orbital regression, and which has been suggested as the source of Saturn's 26.7 degree obliquity (Ward and Hamilton 2004; Hamilton and Ward 2004). Here we examine how Jupiter's ~ 3.1 degree obliquity could be affected by the strong secular spin-orbit resonance arising from this near frequency match. If a portion of the current obliquity is forced by Uranus, this allows for a new constraint on Jupiter's moment of inertia.
This work is supported by NASA's Planetary Geology and Geophysics Program.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.