James Webb Space Telescope Feed Post

Hot Gas Giant Exoplanet WASP-39 b Transit Light Curve (NIRSpec)

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. Read more: science.nasa.gov/missions/webb/nasas-webb-investigates-et... Credits: Illustration: NASA, ESA, CSA, Ralf Crawford (STScI) Image Description: At the top of the infographic is a diagram showing a planet transiting (moving in front of) its star. Below the diagram is a graph showing the change in relative brightness of the star-planet system over 7 hours. The diagram and graph are aligned vertically to show the relationship between the geometry of the star-planet system as the planet orbits, and the measurements on the graph. The infographic shows that the brightness of the system remains steady until the planet begins to transit the star. It then decreases until the planet is directly in front of the star. The brightness increases again until the planet is no longer blocking the star, at which point it levels out. Image & Description by NASA