Energetic neutral atoms as the explanation for the high velocity hydrogen around HD 209458b
SELSIS, Franck
Centre de Recherche Astrophysique de Lyon [CRAL]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
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Centre de Recherche Astrophysique de Lyon [CRAL]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
SELSIS, Franck
Centre de Recherche Astrophysique de Lyon [CRAL]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
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Centre de Recherche Astrophysique de Lyon [CRAL]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Language
en
Article de revue
This item was published in
Nature. 2008, vol. 451, n° 7181, p. 970-972
Nature Publishing Group
English Abstract
Absorption in the stellar Lyman-$\alpha$ (Ly-$\alpha$) line observed during the transit of the extrasolar planet HD 209458b reveals high velocity atomic hydrogen at great distances from the planet. This has been interpreted ...Read more >
Absorption in the stellar Lyman-$\alpha$ (Ly-$\alpha$) line observed during the transit of the extrasolar planet HD 209458b reveals high velocity atomic hydrogen at great distances from the planet. This has been interpreted as hydrogen atoms escaping from the exosphere of the planet, possibly undergoing hydrodynamic blow-off, being accelerated by stellar radiation pressure. However, around solar system planets the production of energetic neutral atoms from charge exchange between solar wind protons and neutral hydrogen from the exospheres has been observed, and should also occur at extrasolar planets. Here we show that the measured transit-associated Ly-$\alpha$ absorption can be explained by the interaction between the exosphere of HD 209458b and the stellar wind, and that radiation pressure alone cannot explain the observation. This is the first observation of energetic neutral atoms outside the solar system. Since the stellar wind protons are the source of the observed energetic neutral atoms, this provides a completely new method of probing stellar wind conditions, and our model suggests a slow and hot stellar wind near HD 209458b at the time of the observation.Read less <
Origin
Hal imported