Luminosity per unit mass (scaled to 1MJ) vs. entropy from numerical integrations. The lines correspond to surface isotherms ﹩T_{\mathrm{deep}\,}( \mathrm{K}\,) =500﹩ (solid black), 1000 (dotted red), 2500 (short‐dashed green), 3000 (long‐dashed blue), and 3500 (dot‐short‐dashed cyan). The lines for ﹩T_{\mathrm{deep}\,}=1500﹩ and 2000 K overlie those for ﹩T_{\mathrm{deep}\,}=1000﹩ K (see Fig. 4). Three masses ﹩M/ M_{\mathrm{J}\,}=0.32﹩, 1.0, and 3.2 are plotted but closely overlie each other (except the largest masses at low entropies, which are never reached), showing that ﹩L/ M﹩ is independent of mass at fixed S and ﹩T_{\mathrm{deep}\,}﹩.