Astronomers find hydroxyl radical in exoplanet's atmosphere for the first time

Wikimedia Commons, Astrobiology Center
Wikimedia Commons, Astrobiology Center

Astronomers have for the first time found a hydroxyl radical (OH) in the atmosphere of an exoplanet - it was found on the dayside of ultra-hot Jupiter WASP-33b. IT is assumed that OH is formed as a result of the photoionization of water vapor. The article is published in The Astrophysical Journal.

Hot Jupiters are gas giants that are very close to their stars. This allows not only easy enough to detect them, but also to investigate their atmospheres, in particular the structure, chemical composition, wind speed at the equator. For scientists, hot Jupiters are of interest both in terms of the dynamics and composition of their atmospheres, and the riddles of the appearance of such objects.

WASP-33b orbits a star of the Delta Shield type, which is located 378 light-years from the Sun in the constellation Andromeda. The exoplanet belongs to the category of ultra-hot Jupiters, a year on it lasts only 29 hours, and the orbit is almost perpendicular to the plane of the star. The temperature of the outer layers of the planet on its daily side is estimated at 3,398 kelvin, its mass is 2.1 mass of Jupiter, and the radius is 1.6 radius of Jupiter. Earlier observations of WASP-33b first detected its stratosphere and then found aluminum oxide in its atmosphere.

A team of astronomers led by Stevanus Nugroho of the Royal University of Belfast published observations of WASP-33b in the near-infrared range using a spectrograph mounted on the 8.2-meter Subaru telescope. Scientists were interested in the composition of the exoplanet's atmosphere on its daytime side.

As a result, scientists for the first time discovered the radiation of a hydro-strong radical in the atmosphere of an exoplanet. Previously, it was found in the Earth's atmosphere, on the surface of the Moon, as well as in the magnetospheres of Saturn, Venus, and Mars. IT is one of the most important radicals that determine the chemistry of the atmospheres of exoplanets, it is assumed that it is formed as a result of photolyzed H2O ultraviolet radiation from the star. Observational data fit well into theoretical models, so OH, along with CO, should be one of the most common molecules in the atmospheres of hot Jupiters, and it should be considered in observations.

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