When JWST was launched on Christmas Day in 2021 as the most powerful infrared telescope to date, it promised to revolutionize exoplanet science by, for the first time, allowing the detection of molecules that are important biosignatures, such as water, oxygen, methane, and carbon dioxide. Detection of such atmospheric gases is made possible by a suite of JWST’s spectrometers, including the Near Infrared Imager and Slitless Spectrograph (NRISS, 0.6 – 5 µm) and Near-Infrared Spectrograph (NIRSpec, 0.6 – 5.3 µm), that cover wavelengths sensitive to water, oxygen, methane, and carbon dioxide. JWST also includes the Mid-InfraRed Instrument (MIRI, 4.9 – 28.8 µm) that allows the detection of distant galaxies, newly forming stars, and comets in the Kuiper Belt.

A new study by the JWST Transiting Exoplanet Early Release Science team, led by Natalie Batalha (UCSC) and including over 300 scientists, reported the first detection of carbon dioxide in the atmosphere of exoplanet WASP-39b using NIRSpec data. On July 10, 2022, JWST observed WASP-39, a Sun-like star 700 light-years away. Over eight hours, JWST measured the star’s brightness using the transit method at over 100 wavelengths. In the transit method, plots of wavelength versus the amount of light blocked (compared to the baseline when no planets or planetary atmospheres block light from the star) reveal dips due to light absorption from different molecules. In the transit of WASP-39b, a hot Jupiter-type gas giant exoplanet orbiting WASP-39, a dip was observed at 4.3 µm consistent with the presence of carbon dioxide. Laura Kreidberg (Max Planck Institute for Astronomy, Germany) remarked, “The exoplanet community has been searching for the signature of carbon dioxide for decades. With the extraordinary new capability of JWST, it will be possible to routinely detect carbon dioxide in the atmospheres of hot Jupiters, as well as smaller, cooler planets more like our own Earth.” READ MORE