The stability and dynamics of planets in tight binary systems

Lamya A. Saleh, Frederic A. Rasio

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Planets have been observed in tight binary systems with separations less than 20 AU. A likely formation scenario for such systems involves a dynamical capture, after which high relative inclinations are likely and may lead to Kozai oscillations. We numerically investigate the fate of an initially coplanar double-planet system in a class of binaries with separation ranging between 12 and 20 AU. Dynamical integrations of representative four-body systems are performed, each including a hot Jupiter and a second planet on a wider orbit. We find that, although such systems can remain stable at low relative inclinations (≲40°), high relative inclinations are likely to lead to instabilities. This can be avoided if the planets are placed in a Kozai-stable zone within which mutual gravitational perturbations can suppress the Kozai mechanism. We investigate the possibility of inducing Kozai oscillations in the inner orbit by a weak coupling mechanism between the planets in which the coplanarity is broken due to a differential nodal precession. Propagating perturbations from the stellar companion through a planetary system in this manner can have dramatic effects on the dynamical evolution of planetary systems, especially in tight binaries and can offer a reasonable explanation for eccentricity trends among planets observed in binary systems. We find that inducing such oscillations into the orbit of a hot Jupiter is more likely in tight binaries and an upper limit can be set on the binary separation above which these oscillations are not observed.

Original languageEnglish (US)
Pages (from-to)1566-1576
Number of pages11
JournalAstrophysical Journal
Issue number2
StatePublished - 2009


  • Binaries: close
  • Celestial mechanics
  • Methods: N-body simulations
  • Planetary systems

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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