Effect of the core mass on the evolution of Jupiter and Saturn. The calculations use the SR2018 phase diagram with T_offset = 350 K. Top panel: present-day helium mass fraction as a function of pressure. The black dot shows the Galileo measured value. Middle panel: effective temperature as a function of age. Black dots show the measured effective temperature. Bottom panel: planet’s radius as a function of age. The black dashed lines correspond to homogeneous evolution calculations. Black dots show the measured radii and the errorbar the uncertainty in age.