The main science goals of the CHEOPS mission will be to measure the bulk density of exoplanets with sizes/masses in the super-Earth – Neptune range orbiting bright stars, and to select the optimal targets for future in-depth characterisation studies of exoplanets in these mass and size ranges. With an accurate knowledge of masses and radii, CHEOPS will set new constraints on the structure and therefore on the formation and evolution of planets in this mass range.
In particular, CHEOPS will:
- Perform first-step characterisations of super-Earths, by measuring the radii and densities in a planetary mass range for which only a handful of data exist and to a precision never achieved before, and by identifying planets with significant atmospheres as a function of their mass, distance to the star, and stellar parameters. The presence (or absence) of large gaseous envelopes bears directly on fundamental issues such as runaway gas accretion in the core accretion scenario or the loss of primordial H/He atmospheres.
- Obtain new insights into the physics and formation processes of Neptune-like planets by measuring accurate radii and densities for these planets, deriving minimum values for their gas mass fractions, and inferring possible evolution paths.
- Provide suitable targets for future ground-based (e.g., E-ELT) and space-based (e.g., JWST) facilities with spectroscopic capabilities. With well-determined radii and masses, the CHEOPS planets will constitute the best sample of targets for such future studies, both within the solar neighbourhood and spread over the whole sky.
- Probe the atmospheres of known 'hot Jupiters' in order to study the physical mechanisms and efficiency of the energy transport from the dayside to the night side of the planet.
CHEOPS will also offer 20% of open time to the community, which will be allocated through competitive scientific review.