Transit depth evolution (ΔF) as a function of time for two models with planetary cores of 1 M_⊕ (dashed blue) and 10 M_⊕ (solid red), both located at 0.07 au from a Solar-type star. The curves show the expected signal in ppm due to Kelvin–Helmholtz contraction of a captured H/He envelope under radiative cooling. After ∼30 years, the low-mass planet reaches ΔF ≈ 272 ppm, while the higher-mass planet yields ΔF ≈ 28 ppm, owing to its stronger surface gravity compressing the envelope.