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Hot Jupiters from secular planet–planet interactions

Nature volume 473, pages 187189 (12 May 2011) | Download Citation

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Abstract

About 25 per cent of ‘hot Jupiters’ (extrasolar Jovian-mass planets with close-in orbits) are actually orbiting counter to the spin direction of the star1. Perturbations from a distant binary star companion2,3 can produce high inclinations, but cannot explain orbits that are retrograde with respect to the total angular momentum of the system. Such orbits in a stellar context can be produced through secular (that is, long term) perturbations in hierarchical triple-star systems. Here we report a similar analysis of planetary bodies, including both octupole-order effects and tidal friction, and find that we can produce hot Jupiters in orbits that are retrograde with respect to the total angular momentum. With distant stellar mass perturbers, such an outcome is not possible2,3. With planetary perturbers, the inner orbit's angular momentum component parallel to the total angular momentum need not be constant4. In fact, as we show here, it can even change sign, leading to a retrograde orbit. A brief excursion to very high eccentricity during the chaotic evolution of the inner orbit allows planet–star tidal interactions to rapidly circularize that orbit, decoupling the planets and forming a retrograde hot Jupiter.

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Acknowledgements

We thank D. Fabrycky and H. Perets for discussions. S.N. acknowledges support from a Gruber Foundation Fellowship and from the National Post Doctoral Award Program for Advancing Women in Science (Weizmann Institute of Science). Simulations for this project were performed on the HPC cluster fugu funded by an NSF MRI award.

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Affiliations

  1. Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, Evanston, Illinois 60208, USA

    • Smadar Naoz
    • , Will M. Farr
    • , Yoram Lithwick
    • , Frederic A. Rasio
    •  & Jean Teyssandier

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Contributions

S.N. performed numerical calculations with help from J.T. All authors developed the mathematical model, discussed the physical interpretation of the results and jointly wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Smadar Naoz.

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https://doi.org/10.1038/nature10076

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