For the first time, an asymmetry of the atmosphere of both hemispheres was discovered on an exoplanet with the density of cotton.

It is surprising to discover the atmosphere of a planet hundreds of light years away from us, but even more surprising to detect the difference between the characteristics of the atmosphere of its hemispheres: the western and eastern. Thanks to the space observatory. James Webb made this possible.

An artist’s impression of an exoplanet with an asymmetric atmosphere. Image source: University of Arizona

The discovery is even more interesting given the relatively low temperature of the exoplanet WASP-107b. It is colder than its usually hotter relatives of the “hot Jupiter” class, but much hotter than the giant planets of the Solar System. The average surface temperature of the exoplanet WASP-107b barely reaches 480 °C. For observations using Webb’s infrared instruments, this means that the planet’s temperature is not sufficient for spectral analysis of its atmosphere through the radiation of the exoplanet itself. Webb can study a planet’s atmosphere only as the planet passes across the disk of its star, when it is illuminated by its radiation.

Overall, exoplanet WASP-107b is extremely strange. It was discovered in 2017 at a distance of 200 light years from Earth in the constellation Virgo. WASP-107b is roughly the same size as Jupiter, but its mass is only 12% or less of that gas giant. This makes the exoplanet as plump as cotton. Among the more than 5,000 exoplanets discovered by scientists, there are less than a dozen such “chubby” planets. The planet rotates very close to its star (several times closer than Mercury in relation to the Sun) and is in its tidal lock – always facing one side to the star. At the same time, the star’s radiation power is not enough to heat the planet to the point of losing its atmosphere.

One of the features of such planets is a very inflated atmosphere. A new study led by a scientist from the University of Arizona has discovered for the first time that exoplanet WASP-107b has an asymmetric atmosphere, divided into hemispheres to the east and west, which determines its climate and climatic behavior. This discovery makes it possible to clarify models of the structure and behavior of such cool planets and provides data that scientists have never previously obtained.

«We cannot directly observe almost all exoplanets, let alone know what is happening on one side compared to the other, say the authors of the work. “For the first time, we can get a much more definitive understanding of what is happening in the atmosphere of an exoplanet.”