What Did NASA’s Webb Discover About WASP-39 b?

Researchers using NASA’s James Webb Space Telescope have confirmed differences between the eternal morning and evening atmospheres of the exoplanet WASP-39 b. This giant planet, with a diameter 1.3 times greater than Jupiter and similar mass to Saturn, orbits a star about 700 light-years away from Earth. Tidally locked to its parent star, WASP-39 b has a constant dayside and nightside.

How Did Scientists Measure the Atmospheric Differences?

Using Webb’s Near-Infrared Spectrograph (NIRSpec), astronomers observed a temperature difference between the eternal morning and evening atmospheres, with the evening being hotter by roughly 300°F (about 200°C). They also noted varying cloud cover, with the morning side likely being cloudier than the evening side.

What Techniques Were Used to Study WASP-39 b’s Atmosphere?

The team analyzed the 2- to 5-micron transmission spectrum of WASP-39 b, studying the exoplanet’s terminator, the boundary separating the planet’s dayside and nightside. By comparing starlight filtered through the planet’s atmosphere to unfiltered starlight, they gathered information about temperature, composition, and other properties.

What Did the New Analysis Reveal?

The new analysis built two different spectra from the terminator region, splitting the day/night boundary into two semicircles. Data revealed the evening as significantly hotter, at 1,450°F (800°C), compared to the morning at 1,150°F (600°C).

How Precise Was Webb in These Observations?

Webb’s sensitivity across near-infrared wavelengths and stable photometric sensors allowed for the precise detection of these differences. Any tiny movement in the instrument or observatory could have limited this ability, but Webb's design ensured the necessary precision.

What Do We Learn About the Atmosphere and Weather Patterns?

Extensive modeling of the data allows researchers to investigate the structure of WASP-39 b’s atmosphere, including cloud cover and temperature variations. The analysis suggests gas circulation around the planet as the main cause of the temperature difference, with powerful equatorial jet streams moving hotter gas from the dayside to the evening terminator.

What Are the Implications for Future Studies?

This analysis provides 3D information about WASP-39 b’s atmosphere, a benchmark for studying other tidally locked hot Jupiters. Future studies will apply similar methods to investigate atmospheric differences in other exoplanets as part of Webb Cycle 2 General Observers Program 3969.

Explore More with the James Webb Space Telescope

WASP-39 b was one of the first targets analyzed by Webb as it began regular science operations in 2022. The data from this study, part of the Early Release Science program 1366, showcases Webb’s full potential in space science exploration.

POLL TIME

Stay tuned for more exciting discoveries from NASA’s James Webb Space Telescope! 🚀🔭