Overview
- JWST transit spectra of TOI-5205 b detected methane and hydrogen sulfide, revealing an atmosphere poorer in heavy elements than its M-dwarf host.
- Interior models indicate the planet holds a large reservoir of heavy elements deep inside, up to about 100 times the atmospheric level, implying weak mixing.
- The planet’s deep transit, blocking about 6% of starlight, gave an unusually strong signal for precise atmospheric measurements.
- Because the host star is heavily spotted, the team refined correction methods for starspot contamination that are now being applied to other JWST observations.
- The finding challenges standard formation models for giant worlds around small stars, a core question for the GEMS survey that targets giant planets orbiting M-dwarfs.