Since the discovery of the first planet to orbit a star other than the Sun in 1995, we have realized that planets and planetary systems are much more diverse than we imagined. Such distant worlds – exoplanets – give us the opportunity to study how planets behave in different situations. And studying their atmosphere is an important piece of the puzzle.

NASA’s James Webb Space Telescope (JWST) is the largest telescope in space. Launching in Christmas 2021, this tool is the perfect tool to explore these worlds. Now, my colleagues and I have used the telescope to discover the chemical composition of an exoplanet for the first time. And data published as preprints (that is, those that have not yet been published in a peer-reviewed journal) offer some surprising results.

Many exoplanets are too close to their parent stars for even this powerful telescope to distinguish them. But we can use a trick by watching a planet pass in front of its star. During the transit, the planet blocks a small portion of the starlight, and an even smaller portion of the starlight is filtered through the outer layers of the planet’s atmosphere.

Gases in the atmosphere absorb some of the light and leave fingerprints in the form of darkening certain colors or wavelengths in starlight. Because the JWST is an infrared telescope, it is particularly suitable for studying the atmospheres of exoplanets. Most gases in the atmosphere, such as water vapor and carbon dioxide, absorb infrared light rather than visible light. Source