To aid in the physical interpretation of planetary radii constrained through observations of transiting planets , or eventually direct detections , we compute model radii of pure hydrogen-helium , water , rock , and iron planets , along with various mixtures .
Masses ranging from 0.01 Earth masses to 10 Jupiter masses at orbital distances of 0.02 to 10 AU are considered .
For hydrogen-helium rich planets , our models are the first to couple planetary evolution to stellar irradiation over a wide range of orbital separations ( 0.02 to 10 AU ) through a non-gray radiative-convective equilibrium atmosphere model .
Stellar irradiation retards the contraction of giant planets , but its effect is not a simple function of the irradiation level : a planet at 1 AU contracts as slowly as a planet at 0.1 AU .
We confirm the assertion of Guillot that very old giant planets under modest stellar irradiation ( like that received by Jupiter and Saturn ) develop isothermal atmospheric radiative zones once the planet ’ s intrinsic flux drops to a small fraction of the incident flux .
For hydrogen-helium planets , we consider cores up to 90 % of the total planet mass , comparable to those of Uranus and Neptune .
If ‘ ‘ hot Neptunes ’ ’ have maintained their original masses and are not remnants of more massive planets , radii of \sim 0.30-0.45 R _ { \mathrm { J } } are expected .
Water planets are \sim 40 - 50 % larger than rocky planets , independent of mass .
Finally , we provide tables of planetary radii at various ages and compositions , and for ice-rock-iron planets we fit our results to analytic functions , which will allow for quick composition estimates , given masses and radii , or mass estimates , given only planetary radii .
These results will assist in the interpretation of observations for both the current transiting planet surveys as well as upcoming space missions , including COROT and Kepler .