The telescope’s array of highly sensitive instruments trained on the atmosphere of a “hot Saturn” – a planet as massive as Saturn orbiting a star about 700 light-years away – known as WASP-39 b. The data was analyzed by an international team with more than 100 scientists from around 50 different institutions.
Among the unprecedented revelations is the first detection in an exoplanet atmosphere of sulfur dioxide, a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is created in a similar way.
The new readings also reveal signs of active chemistry in the atmosphere. “This is the first time we have seen concrete evidence of photochemistry (chemical reactions initiated by energetic starlight) in exoplanets,” said Dr Shang-Min Tsai (Department of Physics, University of Oxford), lead author of sulfur dioxide analysis. “I see this as a very promising insight for advancing our understanding of exoplanet atmospheres with JWST.”
Webb also saw carbon dioxide at a higher resolution, providing twice as much data as reported from his previous observations. Other atmospheric components detected by the Webb telescope include carbon monoxide, sodium, potassium and water vapor, confirming previous observations from space and ground-based telescopes, as well as finding additional water elements, at longer wavelengths, that were not ‘had seen before.
Artistic design of the James Webb Space Telescope. Credit: NASA GSFC/CIL/Adriana Manrique Gutiérrez.
The complete list of chemical ingredients in an exoplanet’s atmosphere allows researchers to estimate the abundance of different elements relative to each other, such as the ratios of carbon to oxygen or potassium to oxygen. This will provide insight into how this planet, and perhaps others, formed from the disk of gas and dust surrounding the parent star in its younger years.
Associate Professor of Physics Vivien Parmentier (Department of Physics, University of Oxford), co-author of the five studies in the analysis, said: “By detecting sulfur dioxide, we have access to sulfur atoms for the first time in an atmosphere of ‘an exoplanet. . Together with the detection of carbon dioxide and water giving us access to carbon atoms, this provides a much more holistic view of what the components of this planet might have been.’
The chemical inventory of WASP-39 b suggests that it was significantly bombarded by large rocky bodies, called planetesimals, which over time enriched its atmosphere in rocky material. The data also indicate that oxygen is much more abundant than carbon in the atmosphere, suggesting that WASP-39 b originally formed far from the central star.
As part of the first JWST program, these observations were immediately made public, enabling a very broad community effort involving scientists from around the world. The contributing author, Dr. Jake Taylor (Department of Physics), said: “It was very refreshing to be involved in this community effort that focused on improving early career researchers. The open science approach has led to a culture of transparency and collaboration that we hope will continue into the JWST era.’
The data were captured using JWST’s three instruments that use infrared light to detect chemical fingerprints that cannot be detected in visible light (NIRSpec, NIRCam and NIRISS). To see the light from WASP-39 b, JWST followed 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 absorb different colors of starlight, so the resulting spectrum tells you which molecules are present.
In addition to the University of Oxford, the other UK institutions involved in the analysis were the Universities of Bristol, Exeter, Leicester and Warwick.
The new studies on WASP-39 b are:
NASA’s James Webb Space Telescope made the first identification of sulfur dioxide in the atmosphere of an exoplanet. Their presence can only be explained by photochemistry: chemical reactions triggered by high-energy particles in starlight. Photochemistry is essential to Earth processes key to life such as photosynthesis and the generation of our ozone layer. Image credits: NASA/JPL-Caltech/Robert Hurt; Center for Astrophysics-Harvard and Smithsonian/Melissa Weiss