Free Astronomy Magazine January-February 2023

33 JANUARY-FEBRUARY 2023 gether, provide a broad swath of the infrared spectrum and a panoply of chemical fingerprints inaccessible until [this mission] ,” said Natalie Batalha, an astronomer at the University of California, Santa Cruz, who contributed to and helped coordinate the new research. “Data like these are a game changer.” Among the unprece- dented revelations is the first detection in an exo- planet atmosphere of sulfur dioxide (SO 2 ), a mol- ecule produced from chem- ical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is cre- ated in a similar way. “This is the first time we see con- crete evidence of photochemistry – chemical reactions initiated by ener- getic stellar light – on exoplanets,” said Shang-Min Tsai, a researcher at the University of Oxford in the United Kingdom and lead author of the paper explaining the origin of sulfur dioxide in WASP-39 b’s atmos- phere. To see light from WASP-39 b, Webb tracked the planet as it passed in front of its star, allowing some of the star’s light to filter through the planet’s atmosphere. Different types of chemicals in the atmosphere ab- sorb different colors of the starlight spectrum, so the colors that are miss- ing tell astronomers which mole- cules are present. By viewing the universe in infrared light, Webb can pick up chemical fingerprints that can’t be detected in visible light. Other atmospheric constituents de- tected by the Webb telescope in- clude sodium (Na), potassium (K), and water vapor (H 2 O), confirming previous space- and ground-based telescope observations as well as finding additional fingerprints of water, at these longer wavelengths, that haven’t been seen before. Webb also saw carbon dioxide (CO 2 ) at higher resolution, providing twice as much data as reported from its previous observations. T his illustration shows what exo- planet WASP-39 b could look like, based on current understanding of the planet. WASP-39 b is a hot, puffy gas giant with a mass 0.28 times Jupiter (0.94 times Saturn) and a diameter 1.3 times greater than Jupiter, orbiting just 0.0486 astro- nomical units from its star. The star, WASP-39, is fractionally smaller and less massive than the Sun. Because it is so close to its star, WASP-39 b is very hot and is likely to be tidally locked, with one side facing the star at all times. [NASA, ESA, CSA, Joseph Olmsted (STScI)] ASTRO PUBLISHING