Relationship between the threshold mass M_thrs and radius R_thrs (lines; see text for definitions) compared to masses and radii of observed transiting super-Earths around G-type stars (points with error bars; exoplanets.org (Wright et al. 2011), as of June 29, 2013, ). The dotted (blue), dashed (green), and solid (red) lines represent the M_thrs and R_thrs relationships for orbital periods of 11 days (=0.1 AU), 4 days (=0.05 AU), and 1 day (=0.02 AU), respectively. The dash-dotted (brown) line represents the planet composed of rocks. Note that black points represent planets whose orbital periods are longer than 11days. In those calculations, we have assumed the heating efficiency ε = 0.1 and the initial luminosity L₀ = 1 × 10²⁴  erg  s^-1. “CoR” are short for CoRoT and “Kep” are short for Kepler.