Detection of extreme atmospheric conditions on the exoplanet WASP-39 b with the help of NASA's James Webb Space Telescope: Analysis of differences between the morning and evening sides

Researchers using NASA's James Webb Space Telescope (JWST) have confirmed earlier assumptions about the exoplanet WASP-39 b, which is tidally locked and has a perpetual morning and evening atmosphere. WASP-39 b, a gas giant with a diameter 1.3 times larger than Jupiter and a mass similar to Saturn, orbits a star about 700 light-years from Earth. One side of the planet is always exposed to light, while the other side is always in darkness.

Using Webb's NIRSpec (Near-Infrared Spectrograph), astronomers have discovered a significant temperature difference between the morning and evening sides of the planet. The evening side is warmer by approximately 300 degrees Fahrenheit (about 200 degrees Celsius) compared to the morning side. Additionally, researchers have noted differences in cloud coverage, with the morning side being richer in clouds than the evening side.

The team used a transmission spectrum from 2 to 5 microns to study the terminator, the boundary separating the day and night sides of the planet. The transmission spectrum is created by comparing the star's light filtered through the planet's atmosphere as it moves in front of the star with the unfiltered light of the star detected when the planet is beside the star. This technique allows obtaining information about the temperature, composition, and other properties of the planet's atmosphere.

Néstor Espinoza, an exoplanet researcher at the Space Telescope Science Institute and the lead author of the study, stated: “WASP-39 b has become a sort of benchmark planet in studying exoplanet atmospheres with Webb. Its puffy atmosphere provides a strong signal from the starlight filtered through the planet's atmosphere.”

Earlier research had shown the presence of carbon dioxide, sulfur dioxide, water vapor, and sodium in the atmosphere of WASP-39 b. The new analysis divides the terminator region into two parts, morning and evening, with the evening part being significantly warmer, at a scorching 1,450 degrees Fahrenheit (800 degrees Celsius), while the morning part is relatively cooler, at 1,150 degrees Fahrenheit (600 degrees Celsius).

Further modeling allowed researchers to explore the atmospheric structure, cloud coverage, and reasons for the temperature differences. It was found that winds blowing across the planet play a key role in redistributing heat. Hot gases from the day side flow to the night side, creating strong equatorial jet streams that further enhance the temperature difference between the morning and evening sides.

This analysis provides three-dimensional information about the planet that was previously unavailable. The results, published in the journal Nature, represent a significant step forward in exoplanet research and demonstrate the capabilities of the James Webb telescope in resolving the mysteries of planets beyond our solar system.

Researchers will now apply the same method to study atmospheric differences of other tidally locked hot Jupiters as part of the Webb Cycle 2 General Observers Program 3969. WASP-39 b was among the first targets Webb analyzed when it began regular scientific operations in 2022.

NASA's James Webb Space Telescope is the world's most advanced space observatory, designed to solve the mysteries of our solar system, explore distant worlds around other stars, and study the mysterious structures and origins of the universe.

New perspectives on atmospheric analysis
Thanks to Webb's extremely sensitive instruments, researchers can now obtain detailed chemical profiles of exoplanets, including the detection of new molecules such as sulfur dioxide. These discoveries allow a deeper understanding of the dynamics of exoplanetary atmospheres and their climate systems.

Natalie Batalha, an astronomer at the University of California, Santa Cruz, emphasizes the importance of these data: “This kind of data is game-changing. It allows us to gain insight into atmospheric processes in ways that were not possible before.” Webb's ability to analyze spectra in the infrared opens new possibilities for exploring exoplanets, including smaller, rocky planets like those in the TRAPPIST-1 system.

Researchers hope that further studies will allow a better understanding of the formation and evolution of exoplanets and how they compare to our own solar system. JWST will provide valuable data on the diversity of exoplanetary systems in the coming decades, contributing to our knowledge of the universe and our place in it.

All these insights confirm that the James Webb Space Telescope is a key tool for future astronomical research, providing unprecedented details and enabling new discoveries that change our understanding of the universe.

Source: National Aeronautics and Space Administration