Letter to the Editor

WASP-8b: a retrograde transiting planet in a multiple system ^*,**

D. Queloz¹, D. Anderson², A. Collier Cameron³, M. Gillon⁴, L. Hebb³, C. Hellier², P. Maxted², F. Pepe¹, D. Pollacco⁵, D. Ségransan¹, B. Smalley², A. H. M. J. Triaud¹, S. Udry¹ and R. West⁶

¹ Observatoire Astronomique de l'Université de Genève, Chemin des Maillettes 51, 1290 Sauverny, Switzerland e-mail: Didier.Queloz@unige.ch
² Astrophysics Group, Keele University, Staffordshire, ST55BG, UK
³ School of Physics & Astronomy, University of St Andrews, North Haugh, KY16 9SS, St Andrews, Fife, Scotland, UK
⁴ Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, 17, Bat. B5C, Liège 1, Belgium
⁵ Astrophysics Research Centre, School of Mathematics & Physics, Queens University, University Road, Belfast, BT71NN, UK
⁶ Department of Physics and Astronomy, University of Leicester, Leicester, LE17RH, UK

Received: 12 April 2010
Accepted: 21 June 2010

Abstract

We report the discovery of WASP-8b, a transiting planet of 2.25 ± 0.08 M_Jup on a strongly inclined eccentric 8.15-day orbit, moving in a retrograde direction to the rotation of its late-G host star. Evidence is found that the star is in a multiple stellar system with two other companions. The dynamical complexity of the system indicates that it may have experienced secular interactions such as the Kozai mechanism or a formation that differs from the “classical” disc-migration theory.