Pollux will complement HWO's coronagraph by providing high-resolution spectroscopic and spectropolarimetric characterisation of planet-hosting systems. It will provide new insights into exoplanet formation and evolution, characterisation of the atmospheres and magnetospheres of stars and planets, and star-planet magnetic interactions.
Atmospheric Characterisation
UV transmission spectroscopy during transits probes the upper atmospheres, escape rates, and composition of exoplanetary atmospheres through diagnostics unavailable from the ground.
Star-Planet Interactions
UV emission from magnetospheric interactions between a star and its close-in planets — analogous to the Jupiter-Io system — can be detected with Pollux’s sensitivity and resolution.
Circumplanetary & Protoplanetary Disks
UV emission and absorption features trace gas accretion in protoplanetary disks and reveal disk chemistry at the planet-formation stage.
The UV domain is particularly sensitive to mass-loss and escape from exoplanetary atmospheres — key processes that determine long-term habitability. The Lyman-α line and UV metal lines provide the most direct constraints on atmospheric erosion by stellar radiation, which Pollux will measure at unprecedented spectral resolution.