Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits

To aid in the physical interpretation of planetary radii constrained throughobservations of transiting planets, or eventually direct detections, we computemodel radii of pure hydrogen-helium, water, rock, and iron planets, along withvarious mixtures. Masses ranging from 0.01 Earth masses to 10 Jupiter masses atorbital distances of 0.02 to 10 AU are considered. For hydrogen-helium richplanets, our models are the first to couple planetary evolution to stellarirradiation over a wide range of orbital separations (0.02 to 10 AU) through anon-gray radiative-convective equilibrium atmosphere model. Stellar irradiationretards the contraction of giant planets, but its effect is not a simplefunction of the irradiation level: a planet at 1 AU contracts as slowly as aplanet at 0.1 AU. For hydrogen-helium planets, we consider cores up to 90% ofthe total planet mass, comparable to those of Uranus and Neptune. If "hotNeptunes" have maintained their original masses and are not remnants of moremassive planets, radii of 0.30-0.45 times Jupiter's radius are expected. Waterplanets are ~40-50% larger than rocky planets, independent of mass. Finally, weprovide tables of planetary radii at various ages and compositions, and forice-rock-iron planets we fit our results to analytic functions, which willallow for quick composition estimates, given masses and radii, or massestimates, given only planetary radii. These results will assist in theinterpretation of observations for both the current transiting planet surveysas well as upcoming space missions, including CoRoT and Kepler.Comment: Published in The Astrophysical Journal 2007 April. This revision corrects coefficient errors in equations 7 and 8. Erratum sent to Ap