The large radii of hot Jupiters are attributed to internal heating mechanisms. To distinguish between deep heating and delayed cooling due to surface heating, the thermal evolution model was extended with a parameter capturing both effects. A hierarchical Bayesian analysis of system properties from a uniform catalog revealed that the cooling rate is suppressed by 95–98% compared to simple anomalous heating models. This is most likely explained by significant surface heating just below the radiative-convective boundary, allowing the planet to inflate with only weak deep heating. Ohmic dissipation and temperature advection are key components of atmospheric models. If surface heating dominates, then observed signatures of atmospheric circulation should strengthen up to equilibrium temperatures around 1500 K, peak in the 1500–1800 K range, and weaken at higher temperatures.
Hot Jupiters—exoplanets giants snuggled up to their stars—are mysteriously puffed up. Their radii often exceed standard models by 50–100%. New models, based on transiting data (transit method), flip our understanding: heat doesn't come from the interior but from the upper atmosphere. Think of soup: if you heat only the surface, a thin layer boils while the rest stays cool. Similarly, heat gets trapped at the top, slowing interior cooling by 95–98%. This swelling can persist for eons. Even wilder: at 1500°C winds whip up, but at 1800°C they abruptly stop—like the planet overheats and turns off its own storm.
🎯 Some hot Jupiters complete an orbit around their star in less than an Earth day—on such a planet, a year is shorter than a day!