The James Webb Space Telescope has provided a detailed look at TOI-5205 b, a Jupiter-sized planet orbiting a small red dwarf (M dwarf).
The system is often called “forbidden” because of the obscure or outright impossible nature of its environment. TOI-5205 b is approximately the size of Jupiter, but its host star is only 40% the mass of the Sun.
Because the star is so small, the planet blocks 6% of the star’s light during transit, making it an ideal candidate for atmospheric study.
Current planet formation models struggle to explain how such a massive planet could form around such a small host star.
Unexpected Atmospheric Chemistry
Recent atmospheric analysis has revealed a surprising chemical profile. There are far less heavy elements in the atmosphere than expected. In particular, its metallicity is low compared to the star it orbits, which is contrary to the usual formation pattern.
JWST also detected methane and hydrogen sulfide. According to findings published in Astronomical Journal, The planet as a whole is about 100 times more metal rich than its atmosphere.
“We observed a much lower metallicity than predicted by our models for the planet’s bulk composition… This suggests that its heavier elements moved inward during formation and are no longer mixing in its interior and atmosphere,” Kanodia said.
“In summary, these results suggest a highly carbon-rich, oxygen-poor planetary atmosphere,” he said.
The findings suggest that heavy elements or metals moved inward during the planet’s formation and are not mixing with the upper atmosphere. The results challenge our understanding of the early stages of giant planet formation.
The research is part of the “Red Dwarfs and the Seven Giants” program, which specifically targets rare, giant planets orbiting small M-dwarf stars to refine our models of the universe. TOI-5205 b was first confirmed in 2023.
