Zeng, LiLiZengJacobsen, Stein B.Stein B.JacobsenHyung, EugeniaEugeniaHyungLevi, AmitAmitLeviNava, ChantanelleChantanelleNavaKirk, JamesJamesKirkPiaulet, CarolineCarolinePiauletLACEDELLI, GAIAGAIALACEDELLISasselov, Dimitar D.Dimitar D.SasselovPetaev, Michail I.Michail I.PetaevStewart, Sarah T.Sarah T.StewartAlam, Munazza K.Munazza K.AlamLópez-Morales, MercedesMercedesLópez-MoralesDAMASSO, MarioMarioDAMASSOLatham, David W.David W.Latham2025-02-212025-02-2120210004-637Xhttp://hdl.handle.net/20.500.12386/36132Recent astronomical observations obtained with the Kepler and TESS missions and their related ground-based follow-ups revealed an abundance of exoplanets with a size intermediate between Earth and Neptune (1 R ⊕ ≤ R ≤ 4 R ⊕). A low occurrence rate of planets has been identified at around twice the size of Earth (2 R ⊕), known as the exoplanet radius gap or radius valley. We explore the geometry of this gap in the mass-radius diagram, with the help of a Mathematica plotting tool developed with the capability of manipulating exoplanet data in multidimensional parameter space, and with the help of visualized water equations of state in the temperature-density (T-ρ) graph and the entropy-pressure (s-P) graph. We show that the radius valley can be explained by a compositional difference between smaller, predominantly rocky planets (<2 R ⊕) and larger planets (>2 R ⊕) that exhibit greater compositional diversity including cosmic ices (water, ammonia, methane, etc.) and gaseous envelopes. In particular, among the larger planets (>2 R ⊕), when viewed from the perspective of planet equilibrium temperature (T eq), the hot ones (T eq ⪆ 900 K) are consistent with ice-dominated composition without significant gaseous envelopes, while the cold ones (T eq ≲ 900 K) have more diverse compositions, including various amounts of gaseous envelopes.STAMPAenArticle10.3847/1538-4357/ac31372-s2.0-85122962690https://iopscience.iop.org/article/10.3847/1538-4357/ac3137https://api.elsevier.com/content/abstract/scopus_id/85122962690FIS/05 - ASTRONOMIA E ASTROFISICA