SO Webloquio: Measuring the Magnetic Fields of Exoplanets with Star-Planet Interactions

Planets interact with their host stars through gravity, radiation and magnetic fields. For giant planets orbiting stars within ~20 stellar radii (=0.1 AU for a Sun-like star), magnetic star-planet interactions (SPI) are observable at a range of wavelengths with a variety of photometric, spectroscopic and spectropolarimetric techniques. At such close distances, planets orbit within the sub-alfvénic radius of the star, where magnetic interactions are particularly efficient, allowing for the detection and study of exoplanetary magnetic fields, thus probing their internal dynamics and atmospheric evolution. In this talk, I will provide a review (and preview) of magnetic SPI studies for hot Jupiters orbiting Sun-like stars. As we refine our observational techniques, we can extend them to lower-mass stars where the sub-alfvénic region coincides with the classical habitable zone, giving us a way with future experiments to detect the magnetic fields of potentially habitable planets.