Vertical structure of an exoplanet’s atmospheric jet stream

Ultra-hot Jupiters, an extreme class of planets not found in our Solar System, provide a unique window into atmospheric processes. The extreme temperature contrasts between their day and night sides pose a fundamental climate puzzle: how is energy distributed? To address this, we must observe the three-dimensional structure of these atmospheres, particularly their vertical circulation patterns that can serve as a testbed for advanced global circulation models, for example, in ref. 1. Here we show a notable shift in atmospheric circulation in an ultra-hot Jupiter: a unilateral flow from the hot star-facing side to the cooler space-facing side of the planet sits below an equatorial super-rotational jet stream. By resolving the vertical structure of atmospheric dynamics, we move beyond integrated global snapshots of the atmosphere, enabling more accurate identification of flow patterns and allowing for a more nuanced comparison to models. Global circulation models based on first principles struggle to replicate the observed circulation pattern2 underscoring a critical gap between theoretical understanding of atmospheric flows and observational evidence. This work serves as a testbed to develop more comprehensive models applicable beyond our Solar System as we prepare for the next generation of giant telescopes.