Planets on the edge

Francesca Valsecchi, Frederic A. Rasio

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Hot Jupiters formed through circularization of high-eccentricity orbits should be found at orbital separations a exceeding twice that of their Roche limit a R. Nevertheless, about a dozen giant planets have now been found well within this limit (a R < a < 2 a R), with one coming as close as 1.2 a R. In this Letter, we show that orbital decay (starting beyond 2 a R) driven by tidal dissipation in the star can naturally explain these objects. For a few systems (WASP-4 and 19), this explanation requires the linear reduction in convective tidal dissipation proposed originally by Zahn and verified by recent numerical simulations, but rules out the quadratic prescription proposed by Goldreich & Nicholson. Additionally, we find that WASP-19-like systems could potentially provide direct empirical constraints on tidal dissipation, as we could soon be able to measure their orbital decay through high precision transit timing measurements.

Original languageEnglish (US)
Article numberL9
JournalAstrophysical Journal Letters
Issue number1
StatePublished - May 20 2014


  • planet-star interactions
  • planetary systems
  • planets and satellites: gaseous planets
  • stars: evolution
  • stars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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