Researchers using NASA’s James Webb Space Telescope confirmed that exoplanet WASP-39 b, which is tidally locked to its star, has significant atmospheric differences between its eternal morning and evening sides. The planet, 1.3 times Jupiter’s diameter but similar in mass to Saturn, shows a temperature difference of about 300°F (200°C) between the two sides. The morning side is cloudier, while the evening side is hotter. These findings were made using Webb’s NIRSpec to analyze the 2- to 5-micron transmission spectrum, studying the planet’s terminator.