Mass-radius relationships used in this work compared to the confirmed exoplanets that have a known value of both M_p and ρ (grey dots). Planets for which only M_p sin i is known are not included. Solid black line shows the mass-density relationship for giant exoplanets, obtained from Hatzes & Rauer (2015). The dashed blue line and dotted red line show the mass-density relationship for low-mass exoplanets with volatile-rich and with rocky composition, respectively, obtained from the M_p –R_p equations inOtegi et al. (2020). Coloured squares mark the rocky planets of the Solar System (Mercury in black, Venus in orange, Earth in green, and Mars in red). Coloured dots mark the giant planets of the Solar System (Jupiter in orange, Saturn in yellow, Uranus in light blue, and Neptune in dark blue).