Astrometry and direct imaging
Astrometry and direct imaging techniques are the only self-consistent ones as they provide the complete orbital configuration and masses of the system. Only a few planetary systems have been found to date using these techniques, but they are among some of the most interesting ones (long period orbits and young systems). Moreover, the situation is about to change drastically. The GAIA data release #4 (expected for 2026) will provide the full astrometric orbital solution of thousands of exoplanets, which is very timely for the DDE meeting.
Exomoons, exorings, and trojan systems
Most solar system planets have moons and rings and so we also expect them to exist around exoplanets. Co-orbital bodies (trojan) are also abundant around Jupiter and Neptune. With the current observational technology, we are at the limit of detecting these bodies and structures. Dynamical studies can tell us which planetary systems are the most favorable to look for them.
Formation and evolution of planetary systems
By better understanding how a planetary system was formed and evolved into the currently observed configuration, we can put constraints on the planetary composition and initial planetary disk. We can also determine if the climates of the planets in the habitable zone can be stable over billions of years such that life can develop.
Planets in binary systems
Half of the stars in the Milky Way are in binary systems. In recent years, many planets have been found either in circumbinary configurations or around a star in a very tight binary. The existence of these planets, at the limit of stability, is very intriguing and their understanding can place many constraints on the formation process.
RV-detected multiple systems
The radial-velocity technique was the first to reveal an exoplanet and it is the second most successful one. It is particularly sensitive to large mass planets, which trigger more disruptive gravitational interactions in the system. It is also not limited to planets in the line-of-sight (like the transit technique). Therefore, some of the most unexpected dynamical configurations were found with this technique (e.g., planets with high mutual inclinations or planets in compact binaries). By correctly modeling the planet-planet interactions we can extract the complete dynamical configuration of the orbits (e.g., retrograde planets) and their true masses.
Stability and dynamics of planetary systems
The orbital stability of planetary systems is not straightforward because of chaotic diffusion in the orbits. Mean-motion and/or secular resonances can help to stabilize the systems and hence put constraints on their orbital parameters to be determined from the observations.
Star-planet interactions and exoplanets' characterization
Star-planet interactions shape the orbits of close-in planets, which allow us to derive constraints for their composition. For instance, tidal interactions predict that close-in planets must be deformed and the orbits decay. From these observations it is possible to derive constraints for the inner structure of planets (Love number) and stars (Q-factor).
Synergies between theory and observations
The DDE meeting aims to bring together communities of observers and theoreticians working on exoplanets. Through the exchange of knowledge and difficulties, we hope that it will be possible to develop common strategies to extract the maximum constraints from observational data and theoretical models. It is thus important to review the successful cases and discuss new strategies to improve the interplay between theory and observations in future studies.
TTVs and transit-detected compact systems
The transit technique is the most successful one to detect planets. For single planets it provides a direct estimation of their radius. However, in multi-planet systems, the transit timing variations (TTVs) induced by mutual perturbations can provide additional invaluable information in their masses and densities. They can also reveal the presence of unseen non-transiting planets. It is therefore extremely important to correctly model the TTVs to extract a maximum of constraints on these planetary systems.
