What We Have Been Looking For? Methane and carbon dioxide found in atmosphere of habitable-zone exoplanet

 We keeping aiming our detectors at deep space -111 light years in this instance. We might find similar results if we concentrated on closer star systems but for many astronomers 111 light years is "safely far away"

Image for visual use

https://www.cam.ac.uk/stories/carbon-found-in-habitable-zone-exoplanet

By Sarah Collins
Published 11 September 2023

An international team of astronomers led by the University of Cambridge has used data from the NASA/ESA/CSA James Webb Space Telescope to discover methane and carbon dioxide in the atmosphere of K2-18 b, an exoplanet in the ‘Goldilocks zone’. This is the first time that carbon-based molecules have been discovered in the atmosphere of an exoplanet in the habitable zone.

The results are consistent with an ocean-covered surface underneath a hydrogen-rich atmosphere. The discovery provides a glimpse into a planet unlike anything else in our Solar System, and raises interesting prospects about potentially habitable worlds elsewhere in the Universe.

K2-18 b — which is 8.6 times as massive as Earth — orbits the cool dwarf star K2-18 in the habitable zone and lies 110 light years from Earth in the constellation of Leo. A first insight into the atmosphere of  K2-18 b came from observations with the Hubble Space Telescope but the atmospheric composition has been a subject of debate. The same researchers studied K2-18 b in 2020 and 2021, and identified it as belonging to a new class of habitable exoplanets called ‘Hycean’ worlds which could accelerate the search for life elsewhere. This prompted them to take a more detailed look with JWST, Hubble’s successor.

Using JWST’s higher resolution instruments, this new investigation has definitively identified methane and carbon dioxide in a hydrogen-rich atmosphere on K2-18 b.

The researchers also identified another, weaker, signal in the K2-18 b spectrum. After several analyses, the researchers say that the signal could be caused by a molecule called dimethyl sulphide (DMS). On Earth, DMS is only produced by life, primarily microbial life such as marine phytoplankton, suggesting the possibility of biological activity on K2-18 b. While these signs of DMS are tentative and require further validation, the researchers say that K2-18 b and other Hycean planets could be our best chance to find life outside our Solar System.

The result, which have been accepted for publication in The Astrophysical Journal Letters, will be presented today (11 September) at the First Year of JWST Science Conference in Baltimore, Maryland, USA.