A.9: ARES – Architecture of Resonant Exoplanetary Systems
Exoplanet systems in resonances present many advantages: high-precision mass estimations, observable traces from formation and evolution mechanisms, etc. This project aims to detect and characterise several such systems with rocky planets.
Despite more than 5000 known exoplanets, our knowledge remains very partial for rocky planets (those approximately Earth-sized). Their density – obtained by combining their mass and their radius – is only known for a few dozen of them. In this project we focus on a particular orbital configuration, resonant systems. Two planets around a same star are said to be in resonance when they both describe a whole number of orbits at the same time (for instance 2 and 1). These systems have many advantages: by observing gravitational disturbances between planets, these systems make it possible to evaluate the mass of small planets with great precision. Furthermore, the fine details of the architecture of these systems encode valuable information about the formation processes and evolution of planetary systems, as well as the internal structure of the planets.
Artist representation of TOI-178 (or HD110067): an example of resonant-system. Tracing a link between two neighbour planet at regular time interval along their orbits, create a pattern unique to each couple due to their resonance-chain.
This research work aims to detect and characterise several dozen to a hundred predominantly rocky planets in resonant orbital configuration (the ratio of the orbital periods of the two planets is a rational number). This will not only provide greater insight into the overall architecture of planetary systems, but will also allow us to learn more about rocky planet systems in general. In particular, this will make it possible to provide constraints on the composition of the planets: mass, radius, internal structure, possibility of characterising their atmosphere, etc.; and on the formation and evolution of systems: shape of the protoplanetary disc, migration of planets, evolution by tidal effects, etc. However, the usual detection and characterisation methods are poorly suited to this type of configuration, most of the rocky planets in resonant configuration therefore remain undetectable in our data until adequate methods are invented.
To do this, the project is divided into three axes:
- Development of detection methods adapted to resonant systems and analysis of existing and future data from the main exoplanet survey missions such as Kepler, TESS, and PLATO.
- In-depth characterisation of the detected systems, if possible using ground-based (VLT) or space-based (CHEOPS and JWST) tracking telescopes.
- Development of analytical models of the evolution of resonances under dissipative processes in order to constrain thanks to the observed systems, the internal structure of planets and of their initial proto-planetary discs.
The project makes the most of the existence of data obtained from the monitoring of hundreds of thousands of stars by past and current Kepler and TESS missions, as well as the launch in 2026 of the PLATO space mission which will also monitor more than 200 000 bright stars. The systems detected, by nature multi-planet systems in interesting orbital configurations, are prime targets for follow-up observations with space telescopes including CHEOPS, led by Switzerland and JWST, as well as ground-based telescopes, notably the VLTs as well as the future Extra Large Telescope located in Chile.
