Orbital orientations of exoplanets: HAT-P-4b is prograde and HAT-P-14b is retrograde

Joshua N. Winn, Andrew W. Howard, John Asher Johnson, Geoffrey W. Marcy, Howard Isaacson, Avi Shporer, Gáspár Á Bakos, Joel D. Hartman, Matthew J. Holman, Simon Albrecht, Justin R. Crepp, Timothy D. Morton

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


We present observations of the Rossiter-McLaughlin effect for two exoplanetary systems, revealing the orientations of their orbits relative to the rotation axes of their parent stars. HAT-P-4b is prograde, with a sky-projected spin-orbit angle of λ = -4.9 ± 11.9 deg. In contrast, HAT-P-14b is retrograde, with λ = 189.1 ± 5.1 deg. These results conform with a previously noted pattern among the stellar hosts of close-in giant planets: hotter stars have a wide range of obliquities and cooler stars have low obliquities. This, in turn, suggests that three-body dynamics and tidal dissipation are responsible for the short-period orbits of many exoplanets. In addition, our data revealed a third body in the HAT-P-4 system, which could be a second planet or a companion star.

Original languageEnglish (US)
JournalAstronomical Journal
Issue number2
StatePublished - Feb 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Planet-star interactions
  • Planetary systems
  • Planets and satellites: Formation
  • Stars: Rotation


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