The Formation, Life and Fate of Exo-Neptunian Systems

The formation, life and fate of Neptunian exoplanets combine a wide range of physical effects and lead to a diverse set of planets with unknown evolutionary histories. Do close-in Neptunes reach their locations through high eccentricity migration, disc-driven migration, or a combination of the two? How are their atmospheres and their photo-evaporation affected by these processes, given that the two migration pathways will bring Neptunes to their present location at different ages? What are the observable planet demographics that would allow us to address these questions and build a consistent theoretical picture of the combined processes involved? JWST, TESS and upcoming missions such as PLATO, Roman and Ariel provide timely opportunities to investigate the population of Neptune planets, from very different angles, linking the evolution at short orbital periods to the composition acquired beyond the ice line. We aim to bring together different communities working on Neptunian exoplanets, to allow observations and theory to inform each other and help push towards a unified understanding of these worlds that sit between rocky planets and Jupiter-scale gas giants.

Workshop Aims
- To bring together communities working on exo-Neptune discovery and characterisation, internal and atmospheric structure and composition, formation and evolution.

- To identify key observational conclusions around the current data, such as density distributions, high metallicity atmospheres, structure in the population demographics, and tracers of mass loss, and tie these together into a unified picture of Neptune formation and evolution.

- To provide a particular focus on connecting new observational results with theoretical understanding of Neptune formation and evolution.

- To develop plans for what new observations or simulations are necessary to improve our understanding going forwards. Guide future observing proposals, plans and development to best make use of the full range of present and upcoming instruments, such as JWST, Gaia, ESPRESSO, NIRPS, ANDES, PLATO and Roman.