Mass–radius diagram for young (<1 Gyr) planets with precise age estimates (relative errors <50%). TOI- 1430 b is located at the edge of the Fulton gap; the arrow indicates the final position in the diagram in the next 200 Myr, when it will completely lose its atmosphere. The Zeng et al. (2019) tracks are reported in magenta (dot-dashed lines) in the case of planets composed of 100% Fe, 32.5% Fe+67.5% MgSiO₃ (Earthlike), 50% Earth+50% H₂O, and 99.7% Earth+0.3% H₂; the Lopez & Fortney (2014) tracks for exoplanets with H/He envelopes between 0.01% and 1% are reported in green. Exoplanets with accurate age estimation are color-coded on the basis of the color bar at the top of the figure; square points are the exoplanets with accurate mass measurement, and triangles are the exoplanets with a mass upper limit measurement.