Astronomers have analyzed the atmosphere of WASP-166 b, a hot super-Neptune exoplanet, revealing the presence of water and carbon dioxide. Using data from the James Webb Space Telescope (JWST), observations also detected trace amounts of ammonia. WASP-166 b is located about 368 light-years away and is about seven times as massive and 32 times as massive as Earth. The planet, orbiting its host star at a distance of 0.067 AU every 5.44 days, has an estimated equilibrium temperature of 1,270 K, placing it in the hot Neptune desert.

Results from JWST observations

As Reported Via phys.org, JWST used its Near Infrared Imager and Slitless Spectrograph (NIRISS) and Near Infrared Camera (NIRCam) to study the atmosphere of WASP-166 b. These observations identified water and carbon dioxide as the dominant elements in the spectrum, along with weak signatures of ammonia and cloud-deck pressure. Helium and hydrogen, in an early solar ratio, are thought to make up the rest of the atmosphere. A search for compounds such as carbon monoxide yielded no significant results.

Characteristics of WASP-166 and its planet

WASP-166, the host star of this exoplanet, belongs to the F9V spectral type and is about 20% more massive than the Sun. It is 2.1 billion years old, with a surface temperature of 6,050 K and a metallicity of 0.19 dex. The planet WASP-166 b has a calculated carbon-to-oxygen ratio of 0.282, significantly lower than both the host star (0.41) and the Sun (0.55). Additionally, the planet was reported to have a high atmospheric metallicity of 1.57.

Description of Atmospheric Structure

It was suggested that atmospheric composition could be linked to planetary accretion, core erosion, or photoevaporation. Such findings contribute to understanding the formation and evolution of planets, particularly in regions such as the hot Neptune desert. The study provides insight into the diversity of exoplanetary systems and their unique properties.