Constraining the structure of small-mass planets
The bulk composition and interior structure of a planet (metallic core, silicates, ice, gas) carry the fossil signature of its early formation history and internal evolution. On the low-mass end of the planet-mass distribution, a broad diversity is observed. The detection of transiting Neptunes and super-Earths provide fundamental information to constrain the inner composition of these planets. Even if no unique solution is expected (degeneracy), basic guesses on the chemical species and constraints from planet formation models should allow for at least a partial solution of the problem. In this context, it is of the uttermost importance to precisely measure the radii of small-mass planets. To achieve this goal, it is clear that the next generation of transit surveys must concentrate on bright stars, allowing in the same time for both precise radius measurement and high precision radial-velocity confirmation and mass estimate. The focus of this sub-project is to help three major projects aiming at the detection of small-size transiting planets around bright stars: CHEOPS, NGTS and PLATO.