Studying the origins of warm Jupiters

There is much still to learn about giant planets, in particular those at relatively long orbital period. Present (TESS, CHEOPS) and future planetary missions (PLATO, Ariel) will make a significant contribution to our understanding of these systems.

One unsolved problem is the origins of warm Jupiters (WJs). If WJs formed beyond the snow line, far from their host stars, then migration is required to bring them to their current orbits. There are several hypotheses explaining the migration history and we are exploring observational tests for these hypotheses. In particular, obliquity (the angle between the stellar rotation and planetary orbital axes) is a key tracer of migration history. Dynamically violent, high-eccentricity migration leads to planets in significantly misaligned orbits with large obliquities, whereas disc-driven migration should result in orbits coplanar with the stellar equator. In contrast to the hot Jupiters, the imprint of dynamical migration in WJs should not be erased through tidal interactions with the convective zone of their stars, because they are tidally detached.

Only around 60 transiting warm Jupiters are currently known, only 16 of which have a measured obliquity. We have a VLT/ESPRESSO programme to measure the obliquities of an unbiased sample of eleven WJs, which will greatly increase the size of the measured sample. Our first observations were made earlier this year, and here we present those data, and our preliminary interpretation.