The multiple aspects of Star-Planet Interactions

Star-Planet Interactions (SPIs) encompass a range of physical processes that occur in close-in exoplanetary systems, where the proximity between a star and its planet leads to complex magnetic, gravitational, and atmospheric effects. These interactions can influence both stellar activity and planetary evolution, making them crucial to our understanding of exoplanetary environments, habitability, and observational signatures across multiple wavelengths. One key aspect of SPIs is their impact on the magnetic activity of the host star. Close-in planets, particularly those orbiting magnetically active stars, can modify the star’s magnetosphere, potentially enhancing or suppressing stellar activity through mechanisms such as magnetic reconnection or tidal interactions. This could lead to observable changes in stellar spots, flares, and coronal mass ejections, affecting not only the planet itself but also the broader space weather conditions of the system. On the planetary side, interactions with the stellar magnetic field and wind can generate radio emissions, providing a potential way to detect and characterise exoplanetary magnetospheres. These emissions, similar to auroral radio signals observed in the Solar System (e.g., from Jupiter and its moons), could offer the first direct constraints on exoplanetary magnetic fields, which play a fundamental role in shielding planetary atmospheres from erosion and determining their long-term habitability. In this seminar, I will provide an overview of SPIs and their different manifestations, discussing both the observational evidence and theoretical frameworks used to study these interactions. I will highlight the role of stellar magnetism in shaping SPI signals, explain the challenges in detecting and interpreting these signatures, and discuss how multi-wavelength observations—including optical, X-ray, and radio surveys—are helping us advance our understanding of exoplanetary atmospheres, magnetic fields, and their interaction with their host stars.