Ultra-hot Jupiters, an extreme class of planets not found in our solar system, provide a unique window into atmospheric processes.
![The jet stream probed by sodium. (a) Diagram of the viewing geometry of WASP-121 b during the morning and evening segment (left and right) (not to scale) highlighting the three probing species and their movement direction over the planet’s surface. The polar view is shown with the observer on the bottom and the host star on the top. The parts of the line of sight obscured by the planetary disk are shaded in grey, the night side of the planet is line-hatched. Dark grey indicates likely night-side cloud cover as modelled for WASP-121 b in [20], see Methods 6 for details. The direction of planetary rotation (assumed from synchronous rotation with the star) is shown as a black arrow around the pole, planetary winds are shown as arrows with the colour indicating the probing element (light green: Fe I, yellow: Na I, dark blue: Hα). The rough shape of the atmosphere as derived from Wardenier et al. [18] is shown as black dashed outlines. The trailing and leading limb are marked as well as the evening terminator (e) and the morning terminator (m) where the transition from permanent day- to night-side occurs and vice versa. The angle indicates the angle of the viewing geometry as described in the manuscript. -- astro-ph.EP](https://i0.wp.com/astrobiology.com/wp-content/uploads/2025/02/Vertical-Structure-Of-An-Exoplanet.png?resize=1200%2C712&ssl=1)
Ultra-hot Jupiters, an extreme class of planets not found in our solar system, provide a unique window into atmospheric processes.