Direct imaging stands as the most effective method for studying gas giant exoplanets with orbits beyond 5 au. These massive planets wield considerable influence over the evolution of planetary systems. Therefore, delving into their formation mechanisms and initial orbital distribution is of paramount importance. This endeavour not only refines our planet formation models but also advances our understanding of migration processes, ultimately shedding light on the resulting architectural intricacies of planetary systems.

Advanced extreme Adaptive Optics (xAO)-enabled instruments now provide us the capability to directly observe giant planets in their formative stages, nestled within their birthplace protoplanetary disks during the T Tauri phase, aged less than 5–10 Myr. These observations are possible not just by detecting their thermal emissions in the near- and mid-infrared spectrum (1–5 μm) but also via neutral-H emission lines. These lines are powerful indicators of gas accretion, granting us a direct window into the mechanism of gaseous planet formation.

In the last few years several groups worldwide have been working both on the theoretical and observational side of the planetary gas accretion process, as well as on the development of new instrumentation and techniques optimised for detecting emission from actively accreting protoplanets.

We organise a special session to foster interaction and fruitful discussions between researchers involved in this fast-developing field with the ultimate goal of stimulating collaboration and proposing new ideas, both technological and observational.

The final goal of our session is to draw a state-of-the-art picture of the gas planet accretion physics in terms of both theory and observations and to identify the best research strategies for the community to improve our understanding of this topic.

Programme

We expect contributions for the following aspects of the science case:

• Theoretical framework

  Giant planet formation models, hydrodynamical simulations, models of accretion tracer (neutral-hydrogen-line) emission.

• Observations

  Extreme-AO observations of H I emission in the visible/NIR to probe accretion: e.g., with VLT (SPHERE, ERIS, MUSE), LBT (SHARKs), Magellan (MagAOx), Subaru (SCExAO+CHARIS), HST, KECK (NIRC2, KPIC); evidence for circumplanetary accretion disks in the sub-mm regime, e.g., with ALMA; using JWST to study accreting planets

• New instruments and methods

  Recent and future facilities/techniques for pushing angular resolution and sensitivity of xAO observations at visible–IR wavelengths (e.g., VIS-X, RISTRETTO).

Invited speakers

• Judit Szulágyi (ETH Zürich): review on planet formation and accretion models
• Sasha Hinkley (Exeter University): review on observations

Scientific organisers

Contact