Comparison of the K2-19 planets with known exoplanets. Left: mass-radius diagram of known exoplanets. The gray dots show the transiting planets listed in the NASA Exoplanet Archive (https://exoplanetarchive.ipac.caltech.edu/, Akeson et al. 2013) with planetary radius and mass uncertainties below 20%. The dashed black line shows the sub-Neptune mass-radius relation from Parc et al. (2024). The solid lines represent theoretical models for different compositions (Zeng & Sasselov 2013). Center, idem for planetary radii vs. orbital period (restricted to planets with planetary radius uncertainties below 20%), with exo-Neptunian boundaries from Castro-González et al. (2024a). Right: idem for planetary radii vs. insolation flux. A Gaussian kernel density estimate is shown in different color intensities.