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An Exoplanet Inflated like a Helium Balloon

Artist's impression of the exoplanet HAT-P-11b with its extended helium atmosphere blown away by the star, an orange dwarf star smaller, but more active, than the Sun.
Credit: © Denis Bajram

Artist’s impression of the exoplanet HAT-P-11b with its extended helium atmosphere blown away by the star, an orange dwarf star smaller, but more active, than the Sun.
Credit: © Denis Bajram

Although helium is a rare element on Earth, it is ubiquitous in the Universe. It is, after hydrogen, the main component of stars and gaseous giant planets. Despite its abundance, helium was only detected recently in the atmosphere of a gaseous giant by an international team including astronomers from the University of Geneva (UNIGE), Switzerland. The team, this time led by Genevan researchers, has observed in detail and for the first time how this gas escapes from the overheated atmosphere of an exoplanet, literally inflated with helium. The results are published in Science.

Helium is the second...

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