Abstract

The abundance of discovered planets has led to demographic studies that have revealed population-level trends in planetary properties that are thought to be the imprints of planet formation or evolution. For example, in recent years we have started to discover trends in planetary bulk density as a function of stellar metallicity for low-mass super-Earths and sub-Neptunes, thereby strongly hinting at a compositional link between terrestrial planets and their stars. The feature-specific or population-synthesis based modelling used to explain observed demographics also provide predictions of the nature of planets based on the underlying physical processes. For example, small planets (Rp < 4 R_Earth) might be classified as rocky, water, or gaseous based on their orbital or physical properties. Such properties are often observable, however the planets in previous large-scale studies often lack refined measurements precluding classification of the bodies. Therefore, we must follow-up these planets with specialised instruments to characterise Earth-like planets and advance our understanding of planet formation and evolution.

In this talk, I will present ongoing observational work with the CHEOPS spacecraft to measure the radii of terrestrial planets in order to determine the internal compositional nature of these bodies and test demographic model predictions. Thus, by peering into the interiors of Earth-like planets we can learn about the formation and evolution of planets across the Galaxy.