An international group of astronomers, led by Andrew Mayo from the University of San Francisco, has uncovered the secrets of the atmospheres of the WASP-166 B exoplanet located 368 light years away from Earth using the James Webb orbital telescope. The detailed analysis of the gas shell composition of this unique celestial body has been published on the ARXIV preprint server.
WASP-166 B is seven times larger than Earth and 32 times heavier. It completes a full orbit around its star in just 5.44 days, at a close distance of 0.067 astronomical units. With a surface temperature of 1270 kelvins, it falls into the rare category of celestial bodies known as the “hot desert of Neptune.”
The parent star, WASP-166, is classified as F9V and is around 20% larger and more massive than the sun. With an estimated age of 2.1 billion years, the star has an effective temperature of 6050 kelvins and a metallicity of 0.19 DEX.
Scientists utilized the near infrared spectrograph NIRISS and the NIRCAM camera on the James Webb telescope to observe the atmosphere of WASP-166 B. The analysis revealed a significant presence of water vapor and carbon dioxide dominating the spectrum, along with weak signs of ammonia and determination of the cloud layer pressure.
The main components of the gas membrane include helium and hydrogen in a ratio similar to the primary solar nebula. However, the search for compounds like carbon monoxide yielded no positive results.
Of particular interest is the carbon-to-oxygen ratio of 0.282, lower than that of the parent star (0.41) and solar value (0.55), while the metallicity of the shell is notably high at 1.57.
Researchers suggest that the chemical composition of the atmosphere could be the result of either planetesimal accretion, where small cosmic bodies gradually merge to form a planet, followed by erosion of the nucleus altering the chemical composition, or photo-evaporation, a process where the intense radiation from the star blows atmospheric gases into space, leading to a shift in the remaining atmosphere’s chemical balance.