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Atmospheric chemistry of a Jupiter-like exoplanet revealed

An illustration of the evaporating planet HD 209458b. Credit: ESA, Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS), NASA

Astronomers have gained new insights into the chemical composition of a hot, Jupiter-like exoplanet that orbits a Sun-like star about 161 light-years away from Earth1.

They say the chemical composition of the exoplanet can help understand the physical and potentially life-supporting conditions on such planets.

The discovery of more than 5,000 exoplanets has spurred interest in the search for extraterrestrial life in far-flung regions of space. However, how the planets form remains largely unexplored.

To shed light on it, scientists developed a model to analyse the chemical compositions of HD 209458b, a Jupiter-like gas giant that orbits a Sun-like star HD 209458. The team, which included astronomers Liton Majumdar and Spandan Dash at the National Institute of Science Education and Research in Odisha, created 32 atmospheric composition profiles. They found that the molecules of methane, ammonia, hydrogen cyanide and acetylene are prominent in the planet’s atmosphere.

Their model showed that the exoplanet could have gathered most of its gas from a protoplanetary disc, where temperatures hovered between 88 and 28 kelvin. Initially, the disc was abundant in elemental carbon and oxygen.

Images captured by NASA’s Hubble’s Space Telescope reveal that the planet has methane in its atmosphere. The nearby star heats the planet’s outer atmosphere, causing its gases to escape into outer space.

Researchers estimate that the HD 209458b is losing at least 10,000 tonnes of hydrogen gas per second.



  1. Dash, S. et al. Astrophys. J. 932, 1 (2022) Doi:10.3847/1538-4357/ac67f0

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