Exotic cocktail in atmosphere of extreme exoplanet

Illustration of an exoplanet in space

Illustration: Bibiana Prinoth

Using high-resolution spectroscopy, researchers at Lund University in Sweden have succeeded in mapping the atmosphere of an exoplanet located 322 light years from Earth. The knowledge gained about the hot gas surrounding the Jupiter-like planet is important for the understanding of Earth-like planets.

WASP-189b is a planet outside our own solar system, with a dayside temperature of 3,200 degrees Celsius. The planet is very close to its host star, with a year that lasts for 2.7 days, the time it takes for the planet to orbit the star. WASP-189b is perhaps the most extreme of the approximately 4,300 exoplanets – planets in solar systems other than our own – that have been confirmed to date.

Ever since it was observed in 2020 by the satellite CHEOPS, it has been a subject of interest for astronomers. In a new study published in Nature Astronomy, new facts emerge about the fiery gas giant.

“We used a high-resolution spectrograph to collect star light from the host star, at a time when the light also passed the exoplanet’s gas envelope. After extracting the relevant parts of the spectrum, we were able to link at least nine variants of known substances to the atmosphere of WASP-189b”, says Bibiana Prinoth, a doctoral student in astronomy at Lund University who led the study.

The major discovery is that WASP-189b’s atmosphere contains titanium oxide, which until now could not be detected with certainty in the atmosphere of an ultra-hot gas giant.
In addition to titanium oxide, the researchers found the following elements: iron, titanium, chromium, vanadium, magnesium and manganese.

However, it’s not just this that stands out: by studying the so-called line positions for each element in the atmosphere, the researchers were able to observe that these varied. This showed that WASP-189b has a layered type of atmosphere where three-dimensional chemistry, thermal effects and dynamics in the form of winds play an important role.

“In the past, it has only been possible to analyze the atmospheres of this type of exoplanet with one-dimensional models. In our study, we pave the way for using high-resolution spectrographs to gain a much deeper understanding of exoplanet atmospheres”, says Bibiana Prinoth.

Characterizing the atmosphere of exoplanets has become an important area of ​​research in astronomy and astrophysics. Now that the technical tools are in place, it will be possible for scientists to in detail compare the chemical composition in different types of exoplanet atmospheres, even when it comes to cooler celestial bodies that are more similar to our own planet.

“I am often asked if I think my research is relevant to the search for life elsewhere in the universe. My answer is always yes. This type of study is a first step in this search”, concludes Bibiana Prinoth.

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