The extreme exoplanet has a complex and exotic atmosphere

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An international team made up of researchers from the University of Bern and the University of Geneva as well as the National Research Center (NCCR) PlanetS has analyzed in detail the atmosphere of one of the most extreme planets known. Findings from this hot Jupiter-like planet, which was first characterized using the CHEOPS space telescope, could help astronomers understand the complexity of many other exoplanets, including Earth-like planets.

The Earth’s atmosphere is not a uniform envelope but is made up of distinct layers, each of which has characteristic properties. The lowest layer extending from sea level beyond the highest mountain peaks, for example – the troposphere – contains most of the water vapor and is therefore the layer in which water vapor occurs. most weather phenomena. The layer above it, the stratosphere, is the one that contains the famous ozone layer which protects us from harmful ultraviolet rays of the Sun.

In a new study published in natural astronomyan international team of researchers led by Lund University shows for the first time that the atmosphere of one of the most extreme planets known may also have similar distinct layers, albeit with very different characteristics.

An exotic cocktail for an atmosphere

WASP-189b is a planet outside our own solar system, located 322 light years from Earth. Extensive observations with the CHEOPS space telescope in 2020 revealed among other things that the planet is 20 times closer to its host star than Earth is to the Sun and has a daytime temperature of 3200 degrees Celsius. More recent investigations with the HARPS spectrograph at the La Silla Observatory in Chile have allowed researchers for the first time to take a closer look at the atmosphere of this Jupiter-like planet.

“We measured the light coming from the planet’s host star and passing through the planet’s atmosphere. The gases in its atmosphere absorb some of the light from the stars, just as ozone absorbs some of the sunlight in the Earth’s atmosphere, and thus leave their characteristic “fingerprint”. With the help of HARPS, we were able to identify the corresponding substances,” says Bibiana Prinoth, lead author of the study and a PhD student at Lund University. According to the researchers, the gases that left their fingerprints in WASP-189b’s atmosphere included iron, chromium, vanadium, magnesium and manganese.

An “ozone layer” on an extremely hot planet?

A particularly interesting substance discovered by the team is a gas containing titanium: titanium oxide. Although titanium oxide is very rare on Earth, it could play an important role in WASP-189b’s atmosphere, similar to that of ozone in Earth’s atmosphere. “Titanium oxide absorbs short-wave radiation, such as ultraviolet radiation. Its detection could therefore indicate a layer in the atmosphere of WASP-189b that interacts with stellar irradiation in the same way as the ozone layer does on Earth,” co-author of the study Kevin Heng, professor of astrophysics at the University of Bern and member of the PRN PlanetS, explains.

Indeed, researchers have found hints of such a layer and other layers on the ultra-hot Jupiter-like planet. “In our analysis, we saw that the “fingerprints” of the different gases were slightly modified compared to our expectations. We believe that strong winds and other processes could generate these alterations. And because the fingerprints of different gases have been altered in different ways, we believe this indicates that they exist in different layers – similar to the fingerprints of water vapor and ozone on Earth. would appear differently modified at a distance, as they mostly occur in different atmospheric layers,” says Prinoth. These results could change the way astronomers study exoplanets.

Another way to look at exoplanets

“In the past, astronomers often assumed that the atmospheres of exoplanets existed as a uniform layer and tried to understand it as such. But our results demonstrate that even the atmospheres of intensely irradiated gas giant planets have complex three-dimensional structures,” said study co-author and associate lecturer at Lund University Jens Hoeijmakers.

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


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More information:

Bibiana Prinoth et al, Titanium oxide and chemical inhomogeneity in the atmosphere of exoplanet WASP-189 b, natural astronomy (2022). DOI: 10.1038/s41550-021-01581-z

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