Séminaire IPAG

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HIP 41378: A laboratory for long-period multi-planet systems

jeudi 29 janvier 2026 - 11h00

Salomé Grouffal - IPAG
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Multi-planet systems provide key insights into planet formation and evolution, as their orbital architecture preserves the dynamical history of planets formed in a common protoplanetary disk. Yet, most known systems are compact, short-period, and long-period multiplanet systems with well-measured masses and radii remain rare. The HIP 41378 system is exceptional, hosting five transiting planets with orbital periods up to 1.5 years. It offers a rare opportunity to explore planetary architectures in a regime closer to the Solar System. In this talk, I will present a global analysis of the system based on a decade of high-precision radial-velocity monitoring and space-based photometry, refining the planets’ masses and orbital configuration. I will also discuss the outermost transiting planet of the system, HIP 41378 f, a low-density “super-puff” planet, for which we have updated the planetary parameters and measured the 3D spin-orbit obliquity through a worldwide observational campaign. Its significant misalignment suggests a primordial tilt of the host star relative to the protoplanetary disk. Finally, I will highlight the observational and dynamical challenges posed by long-period, multi-planet systems in the context of the upcoming PLATO mission.

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Salle Manuel Forestini, 414 rue de la piscine, 38400 Saint Martin d'Hères