Mass–radius diagram including all confirmed planets with radii below 4 R_⊕ with masses and radii measured to better than 30% precision (Gray points). Planet parameters are taken from the NASA Exoplanet Archive’s confirmed planets table, as queried on January 20, 2025. The purple pentagon represents the position of HIP 41378 b, while the green diamond represents the postion of HIP 41378 c. The color-coded lines show different theoretical mass–radius relations corresponding to the planet compositions taken from Zeng et al. (2019) (solid lines) and Lopez & Fortney (2014) (dashed lines; 1 Gyr, solar metallicity and incident flux of 10 S_⊕). Also shown are Earth, Uranus and Neptune, for reference.