Five articles, three of which were accepted for publication in the journal “Nature”, available here, here, and here, and two still under peer review, available here and here, report various aspects of a study on the exoplanet WASP-39b. Many researchers participated in various ways in examining observations conducted with the James Webb Space Telescope focused in particular on the atmosphere of this very hot planet. Webb’s various instruments made it possible to detect a number of substances in WASP-39b’s atmosphere such as carbon monoxide, sodium, and potassium. For the first time, sulfur dioxide was detected in the atmosphere of an exoplanet and indicate that photochemical reactions are taking place.
Launched on December 25, 2021, the James Webb Space Telescope has among its purposes to examine the atmospheres of exoplanets. The hope is to find some with characteristics similar to those of the Earth’s atmosphere that makes them potentially habitable. However, WASP-39b is a hot Saturn because it has a mass close to that of Saturn but is so close to its star that its year lasts only four Earth days. It’s interesting from a scientific point of view for the study of gas planets close to their stars and the consequences of this proximity on their atmospheres.
The exoplanet WASP-39b was studied with the Hubble and Spitzer space telescopes, which made it possible to find a lot of water in its atmosphere. The results of that study were published in an article published in “The Astronomical Journal” in December 2017. They include an estimate of a temperature of nearly 800° Celsius on the side of this exoplanet exposed to its star.
The observations of WASP-39b conducted with the James Webb Space Telescope’s various instruments made it possible to discover new substances in its atmosphere. That confirms that it can outperform any other astronomical instrument also due to the fact that it can detect a wider range of infrared frequencies. In addition to water, WASP-39b’s atmosphere contains carbon monoxide, sodium, potassium, and sulfur dioxide.
The presence of sulfur dioxide was discovered for the first time in the atmosphere of an exoplanet and that’s interesting because it’s a compound produced by chemical reactions. On Earth, it’s the natural product of volcanic activity but on a hot Saturn, it can be produced by photochemical reactions caused by stellar radiation which is very strong due to the proximity of WASP-39b. The ozone layer on Earth is produced by those kinds of reactions.
The quantities of various substances present in the atmosphere and the ratios between them offer clues to the formation of a planet. In the case of WASP-39b, the researchers believe that the abundance of sulfur relative to hydrogen indicates that this exoplanet formed at least in part by accretion with various planetesimals merging.
The abundance of oxygen relative to carbon in the atmosphere suggests that WASP-39b formed far from its star and then moved closer. Planetary migration is one of the topics studied by astronomers in recent years and this study offers new clues on this process, confirming the theory that planets can move very close to their star.
The confirmation of the extraordinary performance of the James Webb Space Telescope also in the surveys of the atmospheres of exoplanets aroused the understandable satisfaction of the researchers. WASP-39b is interesting for astronomers and for this reason it was among the first objects of study but many others will follow, including rocky exoplanets to understand if any of them is really the Earth’s twin.
