The time dependence of hot Jupiters' orbital inclinations (Triaud)

Vol. 534
In section 1. Letters

The time dependence of hot Jupiters' orbital inclinations

by A. H. M. J. Triaud, A&A 534, L6

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"Hot Jupiters" (giant planets with short orbital periods) are found to orbit in the equatorial plane of their star, as expected from standard formation models, but they also have orbits that can be highly inclined compared to that plane. In this paper, the author looks at the dependency of the planet's orbital inclination on the stellar age and finds that stars older than about 3 Ga have planets that are all aligned, a configuration that would occur by chance only about 7% of the time. This seems to indicate that hot Jupiters are sent into inclined orbits early in their lifetimes and that the star's spin and planet's orbit progressively realign because of tidal interactions.