The mass-radius relation of exoplanets revisited

¹ Department of Astrophysics, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
e-mail: simonandres.mueller@uzh.ch
² Observatoire de Genève, Université de Genève, 51 Chemin Pegasi, 1290 Versoix, Switzerland

Received: 21 November 2023
Accepted: 31 March 2024

Abstract

Determining the mass–radius (M−R) relation of exoplanets is important for exoplanet characterization. Here, we present a re-analysis of the M−R relations and their transitions using exoplanetary data from the PlanetS catalog, which accounts only for planets with reliable mass and radius determination. We find that “small planets” correspond to planets with masses of up to ~4.4 M_⊕ (within 17%) where R ∝ M^0.27. Planets with masses between ~4.4 and 127 M_⊕ (within 5%) can be viewed as “intermediate-mass” planets, where R ∝ M^0.67. Massive planets, or gas giant planets, are found to have masses beyond 127 M_⊕ and an M−R relation of R ∝ M^−0.06. By analyzing the radius-density relation we also find that the transition from “small” to “intermediate” planets occurs at a planetary radius of ~1.6 R_⊕ (within 3%). Our results are consistent with previous studies’ results and provide an ideal fit for the current measured planetary population.