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.
At a glance
- Spin-orbit angle measurements for six southern transiting planets. New insights into the dynamical origins of hot Jupiters. Astron. Astrophys. 524, A25 (2010) et al.
- Shrinking binary and planetary orbits by Kozai cycles with tidal friction. Astrophys. J. 669, 1298–1315 (2007) &
- Hot Jupiters in binary star systems. Astrophys. J. 670, 820–825 (2007) , &
- Secular evolution of hierarchical triple star systems. Astrophys. J. 535, 385–401 (2000) , &
- Dynamical outcomes of planet-planet scattering. Astrophys. J. 686, 580–602 (2008) , , &
- Evolution of spin direction of accreting magnetic protostars and spin-orbit misalignment in exoplanetary systems. Mon. Not. R. Astron. Soc. (submitted); preprint at http://arxiv.org/abs/1008.3148 (2011) , &
- Formation of hot planets by a combination of planet scattering, tidal circularization, and the Kozai mechanism. Astrophys. J. 678, 498–508 (2008) , &
- Evidence of possible spin-orbit misalignment along the line of sight in transiting exoplanet systems. Astrophys. J. 719, 602–611 (2010)
- Planetary systems in binaries. I. Dynamical classification. Astrophys. J. 683, 1063–1075 (2008) , &
- Hot stars with hot Jupiters have high obliquities. Astrophys. J. 718, L145–L149 (2010) , , &
- Secular chaos and the production of hot Jupiters. Preprint at http://arxiv.org/abs/1012.3475 (2010) &
- On the tidal interaction between protoplanets and the proto-planetary disk. III — Orbital migration of protoplanets. Astrophys. J. 309, 846–857 (1986) &
- Runaway migration and the formation of hot Jupiters. Astrophys. J. 588, 494–508 (2003) &
- Prospects for the characterization and confirmation of transiting exoplanets via the Rossiter-McLaughlin effect. Astrophys. J. 655, 550–563 (2007) &
- Chaotic variations in the eccentricity of the planet orbiting 16 Cygni B. Nature 386, 254–256 (1997) , &
- The equilibrium tide model for tidal friction. Astrophys. J. 499, 853–870 (1998) , &
- Secular perturbations of asteroids with high inclination and eccentricity. Astron. J. 67, 591–598 (1962)
- The evolution of orbits of artificial satellites of planets under the action of gravitational perturbations of external bodies. Planet. Space Sci. 9, 719–759 (1962)
- The orbital evolution of close triple systems — the binary eccentricity. Astron. Astrophys. 77, 145–151 (1979) &
- The stellar three-body problem. Celest. Mech. 1, 200–209 (1969)
- Studies of multiple stellar systems — II. Second-order averaged Hamiltonian to follow long-term orbital modulations of hierarchical triple systems. Mon. Not. R. Astron. Soc. 304, 720–732 (1999) &
- Tidal friction in triple stars. Mon. Not. R. Astron. Soc. 300, 292–302 (1998) , &
- The superorbital variability and triple nature of the X-ray source 4U 1820–303. Mon. Not. R. Astron. Soc. 377, 1006–1016 (2007) , &
- Does Kozai resonance drive CH Cygni? Astron. J. 116, 444–450 (1998) &
- On the relation between hot Jupiters and the Roche limit. Astron. J. 638, L45–L48 (2006) &
- Optical images of an exosolar planet 25 light-years from Earth. Science 322, 1345–1348 (2008) et al.
- Direct imaging of multiple planets orbiting the star HR 8799. Science 322, 1348–1352 (2008) et al.
- Formation of the giant planets by concurrent accretion of solids and gas. Icarus 124, 62–85 (1996) et al.
- Formation and evolution of close-in planets. Astrophys. J. 725, 1995–2016 (2010) , &
- Supplementary Information (112K)
This file contains Supplementary Notes and Data , Supplementary Figure 1 and legend and additional references.