Special steam in distant hell atmosphere

Special steam in distant hell atmosphere

Artist’s rendering of the ultra-hot planet WASP-76b. © International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani

Extreme heat with a mobilizing effect: astronomers have detected several rock-forming elements in the atmosphere of an “ultra-hot Jupiter”. They are therefore probably also part of the building material of cooler gas planets such as Saturn and Jupiter, where they remain hidden. The scientists explain that the evaporated elements in the atmosphere of the hellish exoplanet can also shed light on the composition and formation history of the celestial bodies in our solar system.

Astronomers have meanwhile tracked down thousands of exoplanets and in some cases fundamentally characterized them – now the characteristics of the atmospheres of distant worlds are increasingly becoming the focus of research. The method of transit spectroscopy is used to gain insight into the composition of the gas envelope. It analyzes the light that shines through the atmospheres when exoplanets pass in front of their host star. The spectral signatures of this radiation enable conclusions to be drawn about the occurrence of certain substances.

The focus of the current study by researchers led by Stefan Pelletier from the University of Montreal was a particularly exotic exoplanet located about 634 light-years from Earth in the constellation Pisces: WASP-76b is an extreme example of the category of so-called hot Jupiters, which resemble the gas giant of our solar system but orbit much closer to their host star. The distance is particularly small for WASP-76b – it is about 12 times closer to its star than Mercury is to the Sun. As a result, its atmosphere heats up extremely – to around 2000 degrees Celsius. That heat inflates the planet’s volume to nearly six times that of Jupiter, previous research has shown.

Heat reveals what is hidden

WASP-76b had previously been the focus of atmospheric research and interesting substances were also detected. In the current study, however, Pelletier and his colleagues have now addressed the question of whether special components can also be detected in the gas envelope that would remain hidden in the atmosphere of cooler gas giant planets. The study was based on spectral data provided by the North Gemini Telescope in Hawaii during three passages of the planet in front of its star.

As the team reports, they have now been able to use the signatures in the radiation to detect new elements in the atmosphere of WASP-76b: sodium, potassium, lithium, nickel, manganese, chromium, magnesium, barium, calcium and vanadium. The team explains that these elements found in Earth’s rocks are vaporized by the extreme temperatures in WASP-76b’s atmosphere. As a result, they are also present in gaseous form in the upper layers. As the researchers point out, the results not only shed light on the features of the exotic itself – they also shed light on other giant planets. Because it can be assumed that these elements also contribute to the composition of Jupiter and Co. However, the scientists explain that these planets are too cold to make these elements visible in their atmospheres.

Also informant for solar system research

The detection and relative amounts of these special elements can thus provide important information about our solar system. “It is remarkable that we can learn something about our own solar system from an exoplanet hundreds of light-years away that we would probably never learn otherwise,” says Pelletier. Interestingly, the team further reports that the proportions of many of the elements detected in WASP-76b are consistent with those in our Sun and also in WASP-76b’s central star. This is probably no coincidence, according to the researchers: it’s another indication that gas giant planets like Jupiter and Saturn are more likely to form in a way akin to star formation.

Another important result of the study is the clear detection of vanadium oxide at an exoplanet, the team points out. “This molecule is of great interest to astronomers because it can have a major impact on the atmospheric structure of hot giant planets,” explains Pelletier. “Because vanadium oxide plays a similar role to ozone in that it heats the Earth’s upper atmosphere extremely efficiently.”

Pelletier and his colleagues now want to keep an eye on WASP-76b and target other ultra-hot exoplanets. In this way they hope to be able to gather more information that only these extreme worlds of astronomy can possibly provide.

Source: Association of Universities for Research in Astronomy (AURA), Article: Nature, doi: 10.1038/s41586-023-06134-0

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