James Webb Space Telescope Feed Post

Atmosphere Composition of Exoplanet K2-18 b (NIRISS & NIRSpec)

The James Webb Space Telescope has detected carbon dioxide and methane in the atmosphere of exoplanet K2-18 b, a potentially habitable world 8.6 times as massive as Earth. An abundance of carbon dioxide and methane (along with a shortage of ammonia) is intriguing to astronomers: It supports the idea that this planet may have a water ocean underneath a hydrogen-rich atmosphere. Webb also hinted at a detection of dimethyl sulphide (DMS) on K2-18 b. On Earth, this molecule is only produced by microbial life. Because the detection needs to be confirmed, the team plans to follow up and look for additional evidence of biological activity on the planet. K2-18 b orbits the cool dwarf star K2-18 in the habitable zone (where conditions are right for liquid water to exist) and lies about 120 light-years from Earth. While K2-18 b is in the habitable zone, that does not necessarily mean it can support life. For instance, it may have a hostile environment due to its active star. Its ocean may also be too hot to be habitable. More: go.nasa.gov/462tJOg Illustration: NASA, ESA, CSA, Ralf Crawford (STScI), Joseph Olmsted (STScI). Science: Nikku Madhusudhan (IoA) Image description: A graphic titled “Exoplanet K2-18 b: Atmosphere Composition.” The graphic shows the spectra of the exoplanet K2-18 b from NIRISS and NIRSpec in the form of a graph, with the vertical y-axis labeled as Amount of Light Blocked and the horizontal axis labeled as Wavelength of Light (microns). The data is plotted as dots with vertical error bars. A jagged blue line running through the plot represents the best-fit model. There are semi-transparent magenta, red and green vertical columns also scattered across the plot, indicating where variations in the line represent the presence of methane, carbon dioxide, and dimethyl sulfide combined with other molecules, respectively. Behind the graph is an illustration of the planet and star. The planet is a large fuzzy blue-ish sphere off to the right, taking up half of the background. The red star is smaller at the bottom left of the entire graphic. Image & Description by NASA