Carbon dioxide detected for the first time on an exoplanet

On Thursday, August 25, 2022, by using NASA’s groundbreaking James Webb Space Telescope, a team of astrophysicists reported that they have detected carbon dioxide for the first time in the atmosphere of a planet located outside our solar system. The exoplanet, called WASP-39b, is a hot gas giant with a mass similar to Saturn’s, orbiting a Sun-like star 700 light-years away. 

Besides providing important insights into this planet’s composition and formation, the discovery of carbon dioxide in its atmosphere also offers hope that the Webb telescope may be able to detect and measure carbon dioxide in the thinner atmosphere of smaller rocky planets. 

WASP-39b was first discovered in 2011 by an international consortium called Wide Angle Search for Planets, with the help of a network of robotic telescopes. Unlike the cooler, more compact gas giants from our solar system, this planet orbits very close to its star, completing one circuit in a just over four Earth-days. 

While scientists have already detected the presence of water vapor, sodium, and potassium in its atmosphere, Webb telescope’s unmatched infrared sensitivity has now also confirmed the presence of carbon dioxide, providing the first clear, detailed evidence for carbon dioxide ever detected on an exoplanet.

“As soon as the data appeared on my screen, the whopping carbon dioxide feature grabbed me,” said Zafar Rustamkulov, a graduate student at Johns Hopkins University and member of the James Webb Space Telescope (JWST) Transiting Exoplanet Community Early Release Science team, which conducted this investigation. “It was a special moment, crossing an important threshold in exoplanet sciences.”

“Detecting such a clear signal of carbon dioxide on WASP-39b bodes well for the detection of atmospheres on smaller, terrestrial-size planets,” added team leader Natalie Batalha, a professor of Astrophysics at the University of California, Santa Cruz.

Understanding the composition of a planet’s atmosphere is crucial for clarifying the planet’s origins and evolution. “Carbon dioxide molecules are sensitive tracers of the story of planet formation,” explained team member Mike Line, an associate professor of Planetary Science at the Arizona State University. 

“By measuring this carbon dioxide feature, we can determine how much solid versus how much gaseous material was used to form this gas giant planet. In the coming decade, JWST will make this measurement for a variety of planets, providing insight into the details of how planets form and the uniqueness of our own solar system.”

A detailed description of the composition of WASP-39b’s atmosphere and of what can be inferred about this planet’s formation and evolution will be published soon in the journal Nature.

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By Andrei Ionescu, Earth.com Staff Writer