Gemini North telescope looks into the atmosphere of ultra-hot Jupiter

Using the Gemini North telescope, astronomers conducted a study of the atmosphere of the ultra-hot Jupiter WASP-76b. They were able to detect a number of heavy elements, some of which had never been observed on exoplanets before.

Extreme exoplanet

WASP-76b is a very unusual world. It is a gas giant that orbits a star of spectral class F, located at a distance of 634 light-years from the Sun. Its orbit passes at a distance of about 5 million km from the surface of its host star.

Ultra-hot gas giant WASP-76b in the artist’s image. Source: International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani

Because of such close proximity, the atmosphere of the gas giant is heated to a temperature exceeding 2000 °C. Another consequence is its “bloat”. With a mass of about 90% of the mass of Jupiter, the radius of WASP-76b is about 1.8 times the radius of the largest planet in the Solar System.

Such extreme conditions open up a curious possibility. At such high temperatures, minerals and rock-forming elements that would otherwise remain hidden in the interior of a colder gas giant evaporate and dissipate in the atmosphere. By identifying the presence and relative amounts of these elements, astronomers can then better understand exactly how giant gas planets form.

Secrets of the atmosphere of ultra-hot Jupiter

An international team of researchers decided to test this assumption. For this, they used the MAROON-X instrument mounted on the Gemini North telescope. In total, they observed three WASP-76b transits. 

Gemini North telescope. Source: Peter Michaud/Gemini Observatory

Subsequent analysis revealed eleven chemical elements in the atmosphere of WASP-76b, including sodium, potassium, lithium, nickel, manganese, chromium, magnesium, vanadium, barium, calcium and iron, already known from previous observations. The percentage of most of them roughly corresponds to the chemical composition of the host star. This confirms the hypothesis that gas giants are formed more on the principle of star formation from gas and dust of the protoplanetary disk, rather than during the gradual accretion and collision of dust, rocks and planetesimals, which later form rocky planets.

Another important finding was the discovery of vanadium oxide. This is the first case of finding this compound in the atmosphere of an exoplanet. Vanadium oxide plays about the same role as ozone on Earth, warming up the upper layers of the atmosphere. As a result, the temperature of WASP-76b does not decrease with increasing altitude, but increases.

According to

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