Mass versus maximum radius relationship for different composition of the planetary interior. The heavy red solid line corresponds to an iron-free planet, with an inner mantle made of MgO, and an outer mantle made of Mg₂Si₂O₆. The blue lines are computed assuming a solar Mg/Si and a Fe/Si equal to the solar value (solid line), two times the solar value (dotted line), and five times the solar value (dashed line). The mass-radius relationships for a sphere of silicates and a sphere of water are indicated by thin solid lines (red and blue respectively), and are taken from Wagner et al. (2011). The parameters of some transiting planets are taken from exoplanets.org the 2013 September 16.