The atmosphere of this exoplanet has points in common with that of the Earth

Nearly 5,000 exoplanets have been confirmed to date, including several hundred “ Hot Jupiters “. The latter are comparable in size to Jupiter and Saturnbut are much closer to their star and subsequently also much warmer. An example of a hot Jupiter is WASP-189 b, 322 light years from Earth. Observations made with the Cheops space telescope in 2020 have shown that this planet, 60% larger and twice as massive as Jupiter, is separated from its star by only one-twentieth of the Sun-Earth distance. The star WASP-189, 2.3 times wider and 1.9 times more massive than the Sun, is also hotter than the latter since its surface reaches 7,700°C, against 5,500°C for the Sun. The planet thus reaches 3,200°C on its face. diurnal.

A layered, exotically composed atmosphere

L’atmosphere of the Earth is not a uniform envelope but consists of distinct layers. For example, the lowest layer, the troposphere, contains most of the water vapor and is therefore the seat of most meteorological phenomena. The layer that overhangs it, the stratosphereis the one that contains the famous ozone layer that protects us from the rays ultraviolet harmful from the Sun. In a new study published in the journal Nature Astronomyan international team shows for the first time that the atmosphere of one of the planets most extremes known would also have separate layers.

” We measured the light coming from the planet’s host star and passing through the planet’s atmosphere, says Bibiana Prinoth, lead author of the study and a doctoral student at Lund University, Sweden. ” The gas of its atmosphere absorb some of the light of the star, as the ozone of the Earth’s atmosphere absorbs part of the light from the Sun, and thus leaves its characteristic “fingerprint”.. By using the harps spectrographinstalled on ESO’s 3.6-meter telescope at La Silla (Chile)the researchers were thus able to identify the corresponding substances: these gases included ironfrom titaniumchrome, vanadiumfrom magnesium and manganese.

An “ozone layer” of titanium oxide

One substance discovered by the team is particularly interesting: Titanium oxide absorbs short-wave radiation, such as ultraviolet radiationexplains Kevin Heng, co-author of the study, professor ofastrophysics at the University of Bern and member of the National Research Center PlanetS, both in Switzerland. Its detection could therefore indicate a layer in the atmosphere of WASP-189 b which interacts with stellar irradiation in the same way as the ozone layer does on Earth. “.

The researchers found evidence of such a layer and other layers on the planet: In our analysis, we saw that the “fingerprints” of the different gases were slightly different from our expectations. We think that strong winds and other processes could cause these differences. And since the fingerprints of different gases have been modified differently, we believe this indicates that they exist in different layers, in the same way that the fingerprints of water vapor and ozone on Earth would appear differently modified from a distance , because they mainly occur in different atmospheric layers “explains Bibiana Prinoth.

” Before, the astronomers often assumed that theatmosphere of exoplanets formed an even layer and they were trying to understand it that way. Our results show, however, that even the atmosphere of giant planets intensely irradiated gases have a complex three-dimensional structure », emphasizes Jens Hoeijmakers, co-author of the study and Lecturer associated with Lund University.

” We believe that to be able to fully understand these and other types of planets, including those more similar to Earth, we must appreciate the three-dimensional nature of their atmospheres. This requires innovations in data analysis techniques, modelization computer science and fundamental atmospheric theory concludes Kevin Heng.