A light curve from NASA’s James Webb Space Telescope’s NIRSpec (Near-Infrared Spectrograph) shows the change in brightness from the WASP-39 star system over time as the planet transited the star. This observation was made using NIRSpec’s bright object time-series mode, which uses a grating to spread out light from a single bright object (like the host star of WASP-39 b) and measure the brightness of each wavelength of light at set intervals of time.
The background illustration of WASP-39 b and its star is based on current understanding of the planet from Webb spectroscopy and previous ground- and space-based observations. Webb has not captured a direct image of the planet or its atmosphere.
The artist’s concept displays the terminator of the exoplanet, the boundary that separates the planet’s dayside and nightside. The new analysis of a transmission spectrum of WASP-39 b from Webb’s NIRSpec builds two different spectra from the terminator region, essentially splitting the day/night boundary into two semicircles, one from the evening, and the other from the morning. Astronomers confirmed a temperature difference between the morning and evening, with the evening appearing hotter by roughly 300 Fahrenheit degrees (about 200 Celsius degrees). They also found evidence for different cloud cover, with the morning being likely cloudier than the evening.
