Séminaire IPAG

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From Earthshine to Exoplanets: modeling rocky worlds in reflected light

jeudi 13 novembre 2025 - 11h00

Giulia Roccetti - ESA
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Understanding what makes a planet habitable requires learning how to interpret the faint light reflected by distant worlds. Reflected-light observations provide access to key atmospheric and surface properties and will be central to future efforts to detect and characterize rocky exoplanets. Instruments such as ANDES and PCS on the ELT will soon make it possible to observe non-transiting rocky planets like Proxima b in reflected light, offering an unprecedented opportunity to study their atmospheres and potential habitability. To prepare for such observations, we study Earth as an exoplanet through Earthshine, the sunlight reflected by Earth onto the dark portion of the visible Moon, capturing the planet as a single, unresolved pixel. Using 3D radiative transfer simulations, we model Earth’s atmosphere and surface, including realistic representations of clouds and wavelength-dependent surface albedo maps. By comparing simulations with Earthshine observations, we explore how spectral and polarimetric features, such as the ocean glint and the primary rainbow, can reveal the presence of liquid water and cloud properties. In this talk, I will show how Earth provides a crucial benchmark for the reflected-light characterization of rocky exoplanets, guiding future observations with the ELT and HWO.

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Hôtes : Guillaume Chaverot

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