Mass-radius relationships of rocky exoplanets

TL;DR

This paper discusses how mass and radius measurements of rocky exoplanets inform their internal structure models, highlighting challenges due to degeneracy and measurement errors, and emphasizing the importance of precise radius data.

Contribution

It analyzes the impact of measurement uncertainties on structural models of rocky exoplanets and underscores the need for precise radius measurements for better interior characterization.

Findings

Measurement errors affect density and composition estimates.

Degeneracy in models limits unique interior solutions.

Precise radii are crucial for accurate exoplanet structure models.

Abstract

Mass and radius of planets transiting their host stars are provided by radial velocity and photometric observations. Structural models of solid exoplanet interiors are then constructed by using equations of state for the radial density distribution, which are compliant with the thermodynamics of the high-pressure limit. However, to some extent those structural models suffer from inherent degeneracy or non-uniqueness problems owing to a principal lack of knowledge of the internal differentiation state and/or the possible presence of an optically thick atmosphere. We here discuss the role of corresponding measurement errors, which adversely affect determinations of a planet's mean density and bulk chemical composition. Precise measurements of planet radii will become increasingly important as key observational constraints for radial density models of individual solid low-mass exoplanets or super-Earths.