The Origin of Hot Jupiters Revealed Through Their Age Distribution

Exactly when and how hot Jupiters arrive on their close-in orbits has been a mystery since their first discovery in 1995. The hot Jupiter age distribution may provide valuable insight as the arrival timescale for hot Jupiters differs across migration models. We define a brightness-limited sample of 349 hot Jupiters previously discovered by a range of space and ground-based surveys, and examine the rotation period distribution of the hot Jupiter host stars. We then use these stellar rotation periods as age indicators, since the spin-down rate of Sun-like stars has been calibrated by other work. We compute ages for 58 hot Jupiter systems from the literature using this approach, under the assumption of minimal star-planet tidal interaction. The resulting rotational age distribution suggests a paucity of hot Jupiters younger than 0.8 ± 0.1 Gyr, relative to the abundance of hot Jupiters at older ages. While this result is consistent with a late arrival from high-eccentricity migration, additional work is needed to assess the potential impact of both the Milky Way’s star formation history and completeness of the rotation period catalog on the observed hot Jupiter age distribution.