Maryland today | UMD astronomers are part of the Webb Telescope team that…

NASA’s James Webb Space Telescope has captured the first clear evidence of carbon dioxide in the atmosphere of a planet outside the solar system, according to an international research team that includes two astronomers from the University of Maryland. This observation of WASP-39b, a gas giant planet orbiting a sun-like star 700 light-years away, provides important information about the composition and formation of the planet, and suggests that Webb will be able to measure carbon dioxide in the thinner atmospheres of smaller rocky planets that might bear similarities to Earth.

Associate Professor Eliza Kempton and Assistant Professor Thaddeus Komacek are among the group behind the discovery which has been accepted for publication in the journal Nature. Dozens of other UMD professors and alumni have been involved with the Webb Telescope throughout its 30-year development leading up to its launch last December.

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Kempton and Komacek’s work is part of a larger investigation that includes observations of the planet using multiple Webb instruments to provide the exoplanet research community with robust Webb data as soon as possible, as part of of the Early Release Science program overseen by the space telescope. Baltimore Institute of Science.

Unlike the cooler, more compact gas giants in our outer solar system, WASP-39 b orbits very close to its star – only about one-eighth the distance between the sun and Mercury – completing a circuit in just over four Earth days. . The discovery of the planet, reported in 2011, was made based on ground-based detections of the subtle and periodic attenuation of light from its host star as the planet transits or passes in front of the star.

Transits also allow astronomers to peer into planetary atmospheres using minute differences in the brightness of transmitted light over a spectrum of wavelengths; previous observations from other telescopes, including NASA’s Hubble and Spitzer Space Telescopes, had revealed the presence of water vapor, sodium and potassium in the planet’s atmosphere. Webb’s unparalleled infrared sensitivity also confirmed the presence of carbon dioxide on this planet.

“The reason why we had not been able to definitively identify the CO2 in the atmosphere of WASP-39 b was before that we had never had a telescope capable of producing spectra over the correct wavelength range,” Kempton said. “This discovery shows us that Webb is delivering on its promise to be a transformational facility for astronomical observations.”

The research team used Webb’s near-infrared spectrograph for their observations of WASP-39b. Kempton received an early version of the spectrum – before anyone had labeled its features – and said the presence of carbon dioxide was immediately apparent.

“This is very different from any previous exoplanet atmosphere observations where we would typically go through a much more complex process of comparing many different possible atmosphere models to the data to convince ourselves that we have detected an atom or a specific molecule,” she said. “For the Webb sighting of WASP-39b, the CO2 is just sitting there in plain sight waving ‘Hello! I’m here!'”

No observatory has ever measured such subtle differences in the brightness of so many individual colors in the 3-5.5 micron range in an exoplanet transmission spectrum before. Access to this part of the spectrum is crucial for measuring the abundance of gases like water and methane, as well as carbon dioxide, which are thought to exist in many types of exoplanets.

“The detection of such a clear signal of carbon dioxide on WASP-39 b bodes well for detecting atmospheres on smaller, Earth-sized planets,” said Natalie Batalha of the University of California at Santa Cruz, who leads the team.

Understanding the composition of a planet’s atmosphere is important because it tells us something about the origin of the planet and how it evolved.

“Carbon dioxide molecules are sensitive tracers of the history of planet formation,” said Mike Line of Arizona State University, another member of the research team. “By measuring this characteristic of carbon dioxide, we can determine the amount of solid matter versus the amount of gaseous matter that was used to form this gas giant planet. In the coming decade, JWST [Webb] will make this measurement for a variety of planets, giving insight into the details of planet formation and the uniqueness of our own solar system.

Thanks to Webb’s advanced capabilities, Kempton said the discovery of carbon dioxide in the atmosphere of WASP-39b is the start of a long and successful exploration of exoplanets.

“It’s just the tip of a huge iceberg,” Kempton said. “We expect hundreds of exoplanets to be observed by Webb over the lifetime of the telescope.”

Emily C. Nunez of the College of Computer, Mathematical, and Natural Sciences contributed to this article, which is based on a Space Telescope Science Institute publication.

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