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Fig. 8


Mass-radius diagram of small planets with masses up to 22 M and radius up to 5 R. From top to bottom, the lines denotes different compositions for solid planets in between pure water and pure iron (Brugger et al. 2017). We superimposed the known planets (from the NASA Exoplanet Archive, updated on 2019 May 05) in this mass-radius range where the grey-scale depends on the precision on the mass and radius. We mark the positions of the planets K2-138b, c, d, e, f and g. The uncertainties are the 68.3% confidence interval. For planets f and g, which arenot detected, we overplot the 99% confidence interval on the mass in dashed black.

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