James Webb Telescope maps asymmetrical atmosphere of exoplanet WASP-17b

Astronomers using the James Webb Space Telescope (JWST) have captured the first direct spatial measurements of an asymmetrical atmosphere on the exoplanet WASP-17b. Located approximately 1,300 light-years from Earth, this ‘hot Jupiter’ gas giant does not possess a perfectly spherical atmospheric outline.

By utilizing a new technique called ‘transmission strings,’ an international research team led by Cornell University and the University of Bristol was able to map the uneven contours of the planet. The method allows scientists to measure variations in the distance from the planet's center to the edge of its gaseous envelope during transit, rather than treating the atmosphere as a uniform ring.

The findings, published in Nature Astronomy, reveal that the atmosphere is broadly circular but features a significant asymmetry. Specifically, the evening limb is hotter and more extended than the morning limb. This phenomenon is driven by intense stellar radiation and powerful winds that transport thermal energy from the permanently illuminated dayside to the shadowed nightside, effectively reshaping the planet's atmospheric structure.