James Webb Telescope Discovers Atmospheric Dynamics on Exoplanet WASP-39 b
James Webb Telescope Discovers Atmospheric Dynamics on Exoplanet WASP-39 b
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Artist's rendition of WASP-39 b, based on indirect observations from NASA’s James Webb Space Telescope and other telescopes. This hot, puffy gas giant orbits a G-type star slightly smaller than the Sun, just 4,500,000 miles away. WASP-39 b is tidally locked, creating eternal sunrises and sunsets at its terminator. Credits: Illustration by NASA, ESA, CSA, Ralf Crawford (STScI)
July 15, 2024 - The universe never ceases to amaze, and with NASA’s James Webb Space Telescope (JWST), we continue to unravel its enigmatic secrets. One of the latest discoveries involves the intriguing atmospheric dynamics of the exoplanet WASP-39 b. This distant world, located about 700 light-years from Earth, presents a unique phenomenon: eternal sunrises and sunsets. Using Webb’s advanced observational capabilities, researchers have now confirmed significant differences between the planet’s eternal morning and evening atmospheres.
The Unique Environment of WASP-39 b
WASP-39 b is a gas giant exoplanet, with a diameter 1.3 times that of Jupiter but a mass comparable to Saturn. This colossal planet is tidally locked to its parent star, which means one side perpetually faces the star while the other remains in constant darkness. This unique orientation creates a boundary, known as the terminator, where the eternal day meets the eternal night.
Unveiling Atmospheric Differences
Using Webb’s Near-Infrared Spectrograph (NIRSpec), astronomers have meticulously analyzed the terminator region of WASP-39 b. The data reveals a striking temperature difference between the morning and evening sides, with the evening side being approximately 300 degrees Fahrenheit (about 200 degrees Celsius) hotter. Additionally, the cloud cover varies, with the morning side exhibiting more clouds than the evening.
This detailed analysis was made possible by studying the 2- to 5-micron transmission spectrum of the exoplanet. This technique involves comparing starlight filtered through the planet’s atmosphere during its transit in front of the star to the unfiltered starlight when the planet is beside the star. This comparison provides crucial information about the temperature, composition, and other properties of the atmosphere.
Why the Evening is Hotter
The primary reason for the temperature difference lies in the atmospheric dynamics of WASP-39 b. On a tidally locked planet like this, the gas circulation is intense. The hot gas from the dayside is transported to the nightside via a powerful equatorial jet stream, resulting in a significant temperature and pressure difference. Consequently, the wind speeds on WASP-39 b can reach thousands of miles per hour, with the morning side being cooler due to the inflow of air from the cold nightside, and the evening side being hotter due to the outflow of heated air from the dayside.
Advanced Modeling and Future Research
To understand these atmospheric dynamics better, researchers employed General Circulation Models (GCMs), which are 3-dimensional models similar to those used for predicting weather patterns on Earth. These models revealed that the wind patterns around WASP-39 b are responsible for the observed temperature differences. The evening edge of the planet, being hotter, is slightly puffier, indicating a small swell at the terminator.
The findings from this study not only enhance our understanding of WASP-39 b but also open new avenues for studying other tidally locked hot Jupiters. The team plans to use the same method to investigate atmospheric differences in other exoplanets as part of Webb Cycle 2 General Observers Program 3969.
The Significance of This Discovery
WASP-39 b has become a benchmark in exoplanet atmospheric studies, thanks to the detailed observations from JWST. The discovery of these atmospheric differences adds a new dimension to our understanding of exoplanet climates and the complex interactions between a planet and its star.
The results of this study have been published in Nature, and they underscore the extraordinary precision and capability of the James Webb Space Telescope. Webb continues to be the world’s premier space science observatory, exploring the mysteries of our solar system, distant worlds, and the origins of the universe.
Source - NASA
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A light curve from NASA’s James Webb Space Telescope’s NIRSpec reveals variations in brightness as exoplanet WASP-39 b transits its star. NIRSpec’s bright object time-series mode captures these changes by dispersing starlight through a grating, measuring brightness across different wavelengths over time. Image Credit: NASA, ESA, CSA, Ralf Crawford (STScI)
This transmission spectrum, obtained using Webb’s NIRSpec PRISM bright object-time series mode, illustrates the absorption of near-infrared starlight by the atmosphere of hot gas giant exoplanet WASP-39 b. It reveals clear signatures of water and carbon dioxide, highlighting temperature variations between the morning and evening sides. Credits: Illustration by NASA, ESA, CSA, Ralf Crawford (STScI).
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