Letter to the Editor

The time dependence of hot Jupiters’ orbital inclinations^⋆

Observatoire Astronomique de l’Université de Genève, Chemin des Maillettes 51, 1290 Sauverny, Switzerland
e-mail: amaury.triaud@unige.ch

Received: 15 July 2011
Accepted: 26 September 2011

Abstract

Via the Rossiter-McLaughlin effect, it is possible to measure the sky-projected angle between the stellar spin and a planet’s orbital spin. Observed orbital inclinations have been found to range over all possible angles. A tentative detection of a correlation between the dispersion in spin/orbit angle and the youth of the system is revealed, using spin/orbit measurements for hot Jupiters around stars with masses  ≥1.2 M_⊙ for which age estimates are more accurately determined. The probability of this pattern arising by chance has been computed to be 7%. This appears in accordance with tidal dissipation, where non-coplanar hot Jupiters’ orbits tidally realign. The results suggest they realign within about 2.5 Gyr. For the sample considered, the results imply that hot Jupiters are placed on non-coplanar orbits early in their history rather than late. The events producing these orbits could involve strong planet-planet scattering.