Contributions > By speaker > Ravet Matthieu

Despite the relatively small number of planetary-mass companions detected via direct imag-ing (∼80), they offer a window into the diverse outcomes of planet formation. Among them,COCONUTS-2 b stands out as an extreme outlier—an adolescent super-Jupiter (Teff∼434 K) orbiting its M3 host star at an extraordinary separation of ∼7500 au. The companion's wide orbit challenges conventional formation models, suggesting either outward migration after disk-based formation or formation via cloud fragmentation akin to stellar binaries. Building on prior photometric and spectroscopic studies, we present new JWST/MIRI observations of COCONUTS-2 b, re-analyzed alongside archival data using our updated Forward Modeling Spectral Analysis tool, ForMoSA. By jointly fitting self-consistent atmospheric models, we aim to refine estimates of the companion's physical and chemical properties and assess its likely formation pathway. This work contributes to our understanding of planet formation at the boundary between planetaryand stellar regimes.