Science Gazette

The atmosphere of an extreme exoplanet is complicated and strange


The atmosphere of one of the most severe known planets was studied in great detail by an international team that included academics from the University of Bern and the University of Geneva, as well as the National Centre of Competence in Research (NCCR) PlanetS. The findings from this hot, Jupiter-like planet, which was discovered using the CHEOPS satellite telescope, may aid scientists in better understanding the intricacies of many other exoplanets, including Earth-like planets.

The Earth’s atmosphere is not a homogenous envelope, but rather a collection of unique layers, each with its own set of characteristics. The troposphere, for example, is the lowest layer that stretches from sea level to the highest mountain peaks and contains the majority of the water vapour, making it the layer where most meteorological occurrences occur. The stratosphere, which lies above it, includes the famed ozone layer, which protects humans from the Sun’s damaging UV radiation.

An international team of researchers led by the University of Lund show for the first time that the atmosphere of one of the most extreme known planets may have similarly distinct layers as well — albeit with very different characteristics — in a new study published in the journal Nature Astronomy.

An exotic drink to set the mood

WASP-189b is a planet situated 322 light years from Earth, outside of our solar system. 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, according to extensive measurements made with the CHEOPS satellite observatory in 2020. Recent observations with the HARPS spectrograph at Chile’s La Silla Observatory have enabled astronomers to take a closer look at the atmosphere of this Jupiter-like planet for the first time.

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“We measured the amount of light traveling through the planet’s atmosphere as it came from the planet’s host star. The gases in its atmosphere absorb part of the starlight, similar to how Ozone in Earth’s atmosphere absorbs some of the sunlight, and therefore leave their own ‘fingerprint.’ We were able to identify the related chemicals with the aid of HARPS “Bibiana Prinoth, the study’s principal author and a doctorate student at Lund University, says. Iron, chromium, vanadium, magnesium, and manganese were among the gases that left their imprints on WASP-189b’s atmosphere, according to the researchers.

On a scorching-hot planet, a “Ozone layer”?

One especially intriguing chemical discovered by the scientists is titanium oxide, a gas containing titanium. While titanium oxide is very rare on Earth, it might play a vital function in WASP-189b’s atmosphere, similar to how ozone does in ours. “Short-wave radiation, such as UV light, is absorbed by titanium oxide. Its discovery might point to a layer in WASP-189b’s atmosphere that interacts with solar irradiation in the same way as the Ozone layer does on Earth “Kevin Heng, a professor of astrophysics at the University of Bern and a member of the NCCR PlanetS, explains the study’s co-authorship.

On the ultra-hot Jupiter-like planet, the researchers discovered signs of such a layer, as well as other layers. “In our investigation, we discovered that the ‘fingerprints’ of the various gases were somewhat different from what we expected. We suspect that high winds and other processes are to blame for the changes. And, because different gases’ fingerprints were altered in different ways, we believe this indicates that they exist in different layers — similar to how the fingerprints of water vapour and ozone on Earth would appear differently altered from afar because they mostly occur in different atmospheric layers “Prinoth clarifies. These findings might influence how astronomers examine exoplanets in the future.

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A new perspective on exoplanets

“Astronomers had hitherto believed that planetary atmospheres exist as a uniform layer and attempted to comprehend it as such. However, our findings show that even the atmospheres of massive gas planets with high irradiation contain complex three-dimensional structures “Jens Hoeijmakers, research co-author and associate senior lecturer at Lund University, explains.

“We believe that in order to properly comprehend these and other planets, even those that are more comparable to Earth, we must realize the three-dimensional character of their atmospheres. This will need advancements in data analysis methods, computer modeling, and basic atmospheric theory “Kevin Heng brings the discussion to a close.

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