Evolution of the size of CoRoT-20b (in Jupiter units) as a function of age (in billion years), compared to constraints inferred from CoRoT photometry, spectroscopy, radial velocimetry and stellar evolution models. Green, blue, and yellow regions correspond to the planetary radii and ages that result from stellar evolution models matching the inferred ρ_⋆ – T_eff – [Fe/H] uncertainty ellipse within 1σ, 2σ, and 3σ, respectively. Planetary evolution models for a planet with a solar-composition envelope over a central dense core of variable mass (0, 400, 800, and 1000 M_⊕ as labelled) are shown as dashed lines. These models also assume that 1% of the incoming stellar irradiation is dissipated deep into the interior of the planet.