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EP: Fachverband Extraterrestrische Physik
EP 3: Astrophysik/Astrobiologie
EP 3.6: Talk
Tuesday, February 26, 2013, 15:30–15:45, HS 9
How accurate are estimates of planetary bulk composition as inferred from determinations of planet mass and radius? — •Frank Sohl1, Frank W. Wagner1, and Heike Rauer1,2 — 1DLR Institut für Planetenforschung, Berlin — 2Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Germany
Masses and radii of transit planets are provided by radial velocity and photometric observations. The inferred mean density is the main indicator of the bulk composition of solid planets. Structural models of low-mass exoplanet interiors that are consistent with the thermodynamics of the high-pressure limit are compositionally distinct, but they do partly suffer from inherent degeneracy or non-uniqueness problems. These are related to the imperfect knowledge of the internal differentiation state and/or the possible presence of an optically thick atmosphere. We will discuss the role of mass and radius measurement errors for determinations of a planet’s mean density and bulk chemical composition using calculated relations between radius and mass of solid exoplanets ranging from super-Earths to mini-Neptunes. It is shown that mass-radius relationships based on numerical models of solid exoplanet interiors are sufficiently robust to infer a planet’s bulk composition from accurate determinations of its mean density. Reference: Sohl, F.; F.W. Wagner, H. Rauer (2012), arxiv.org/pdf/1211.3331 .