38 research outputs found

    Tilting Jupiter (a bit) and Saturn (a lot) During Planetary Migration

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    We study the effects of planetary late migration on the gas giants obliquities. We consider the planetary instability models from Nesvorny & Morbidelli (2012), in which the obliquities of Jupiter and Saturn can be excited when the spin-orbit resonances occur. The most notable resonances occur when the s7s_7 and s8s_8 frequencies, changing as a result of planetary migration, become commensurate with the precession frequencies of Jupiter's and Saturn's spin vectors. We show that Jupiter may have obtained its present obliquity by crossing of the s8s_8 resonance. This would set strict constrains on the character of migration during the early stage. Additional effects on Jupiter's obliquity are expected during the last gasp of migration when the s7s_7 resonance was approached. The magnitude of these effects depends on the precise value of the Jupiter's precession constant. Saturn's large obliquity was likely excited by capture into the s8s_8 resonance. This probably happened during the late stage of planetary migration when the evolution of the s8s_8 frequency was very slow, and the conditions for capture into the spin-orbit resonance with s8s_8 were satisfied. However, whether or not Saturn is in the spin-orbit resonance with s8s_8 at the present time is not clear, because the existing observations of Saturn's spin precession and internal structure models have significant uncertainties.Comment: 29 pages, 8 figures, accepted for publication in The Astrophysical Journa
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