DIX Planetary Science Seminar

High-resolution spectrographs have enabled the measurement of stellar spin-orbit misalignment for a population of planets with increasing orbital periods, with recent discoveries unveiling an unexpected trend: warm Jupiters (WJs)—gas giants with orbital periods between 10 and 200 days—exhibit a remarkable degree of spin-orbit alignment with their host stars. This stands in stark contrast to the broad range of stellar obliquities observed in the hot Jupiter population (periods of less than 10 days). Moreover, this alignment persists even for highly eccentric orbits, challenging theoretical models, which typically associate extreme eccentricities with large inclinations. Could such orbital architectures be primordial? If not, what mechanisms could dampen obliquities while allowing eccentricities to remain high? I will discuss recent results from the Warm Jupiters ESPRESSO campaign, which has provided new spin-orbit measurements for over ten WJ systems, highlighting how they challenge existing paradigms, even ruling out several high-eccentricity migration models. I will also explore both qualitative and quantitative scenarios that may explain these systems, including novel formation channels such as coplanar high-eccentricity migration ,and the effect of non-conventional tidal mechanisms. In particular, I will describe how the damping of inertial waves in the convective regions of a star can realign stellar spin without affecting orbital eccentricities or semi-major axes—allowing stellar obliquities to be damped without inducing orbital decay or circularization. This effect may be even more pronounced during the short-lived pre-main sequence phase, when the star is larger, rapidly spinning, and fully convective. These insights not only reshape our understanding of WJ evolution but also provide a compelling case for revisiting tidal dissipation mechanisms in star-planet interactions.