The Mid-Infrared Instrument (MIRI) on NASA’s James Webb Space Telescope was used to create a global temperature map of the hot gas-giant exoplanet WASP-43 b. The map is based on the brightness of 5- to 12-micron mid-infrared light emitted by the planet. Typically, objects that are hotter emit more mid-infrared light.
WASP-43 b is located very close to its star, making it challenging to directly observe the planet. However, scientists can calculate its brightness by measuring the combined light of the star-planet system and then subtracting the light emitted solely by the star. This method allows researchers to determine the temperature distribution on the planet.
The temperature map reveals that WASP-43 b is tidally locked, meaning its rotation rate matches its orbital period, causing different sides to be visible as it orbits around the star. By observing the planet over an entire 19.5-hour orbit, Webb was able to measure both the dayside and nightside temperatures of WASP-43 b. The average temperature on the dayside is around 2,280°F (1,250°C), whereas the nightside temperature is approximately 1,115°F (600°C).
The temperature map also indicates that the nightside of WASP-43 b likely has thick, high clouds. These clouds trap some of the infrared energy, preventing it from escaping into space and causing the nightside to appear cooler than it would without clouds.
