A planet with a lopsided sky: Webb maps the weather on a world 1,300 light-years away

WASP-17b is a scorching giant planet 1,300 light-years away, locked so one side always faces its star. Using the James Webb Space Telescope, astronomers led jointly by Cornell University and the University of Bristol have discovered its atmosphere is lopsided — bulging farther out on one side than the other. The trick was a new technique from Bristol, called transmission strings, which reads the starlight filtering through separate strips of the planet's edge instead of averaging the whole rim into one blur. It shows fierce evening winds hauling heat toward the dark side, swelling the cooler morning sky — confirming what theory predicted about day-night temperature gaps. Lead researcher Dr Lili Alderson's team calls it one of the most detailed three-dimensional pictures yet of an exoplanet's air — a method now ready to aim at the 6,000-plus known worlds beyond our Sun, published in Nature Astronomy.