Evolution of giant planets with dilute cores in MESA

Observations of the Solar System giants, including Juno gravity data from Jupiter and ring seismology of Saturn, indicate that these planets likely have "dilute" or "diffuse" cores, with heavy element mass fraction decreasing gradually with radial distance from the center of the planet. These observations challenge simple layered models of planet interior structure, which have often been adopted in exoplanet and brown dwarf studies for conceptual and computational simplicity. Here, we investigate the effects of a dilute core structure on the evolution of a suite of giant planets, simulated with the 1D stellar evolution code MESA, with particular attention to the cooling rate and luminosity of these planets over time. Alongside, we present the open source modifications we made to MESA to make these simulations possible, including the implementation of an equation of state appropriate to planetary conditions.