ASU researchers reveal the composition of an unlikely exoplanet
An artist's interpretation of WASP-80 b. Image by NASA
Over the past three decades, astronomers have discovered thousands of planets outside our solar system, known as exoplanets. Many of these worlds are unlike those found in our solar system, raising fundamental questions about how planets form and evolve.
Researchers in Arizona State University’s School of Earth and Space Exploration used NASA’s James Webb Space Telescope to investigate one of these unusual exoplanets, WASP-80 b. The gas giant is half the mass of Jupiter and orbits a small star that is only 60% the mass of our sun. Giant planets like WASP-80 b are rarely found around such small stars, possibly because there is not enough material around young, low-mass stars to easily build large planets.
The research study, led by Lindsey Wiser, Michael Line and Luis Welbanks at the School of Earth and Space Exploration, along with collaborators at other institutions, set out to examine WASP-80 b’s atmosphere to determine whether its chemical makeup might hint at a unique method of formation.
The research article is published in a special issue of the Proceedings of the National Academy of Sciences.
“By looking at a 'weird' planet like WASP-80 b, we are really stress-testing our understanding of how planets form, and that improves our predictions for what types of planets exist and how they got there,” said Wiser, who earned her PhD in astrophysics from ASU in spring 2025.
Using JWST, the research team revealed an atmosphere containing water, methane, carbon monoxide, carbon dioxide and possibly ammonia. Interestingly, WASP-80 b’s composition resembles that of more “typical” giant planets around higher-mass stars, leaving unanswered questions about how WASP-80 b got so big. Perhaps there was more mass in the young star-planet system than previously estimated, or maybe the planet started forming earlier than previously thought, giving it more time to grow.
The JWST observations of WASP-80 b collected for this study make up one of the most complete datasets of a single planet cooler than ~1,000 Kelvin. These findings highlight the power of cutting-edge space telescopes for illuminating the compositions of once-mysterious exoplanets.
“It's incredibly exciting to see such a complete dataset for a single planet. Compared to observations with older space telescopes like Hubble and Spitzer, this was the most confidence I've had making conclusions about what a planet's atmosphere is made of,” Wiser said.
“The sheer information content of the data and the capacity for JWST to constantly challenge our understanding of these distant worlds never ceases to amaze me,” said Line, associate professor in the School of Earth and Space Exploration.
This research also underscores Arizona’s leadership in space. ASU’s involvement in JWST science strengthens Arizona’s position as a hub for space science and innovation. Research provides hands-on training for ASU students, helping to develop a skilled workforce for the state’s growing aerospace and technology industries. Additionally, scientific discoveries inspire public interest, reinforcing Arizona’s commitment to education and science engagement.
Overall, this research provides new insights into how the unique population of giant planets around small stars may form, and it highlights the value of the James Webb Space Telescope for expanding our understanding of planetary systems. Exoplanet studies place our solar system in a cosmic context, revealing what makes it unique, or what it might have in common with the growing number of known exoplanetary systems.
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