The origin of hydrogen around HD 209458b.
basic_science · Level V
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- Record sourced from PubMed, PMID 19005500.
- Also identified by DOI 10.1038/nature07402.
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Abstract
Using numerical simulation, Holmström et al. proposed a plausible alternative explanation of the observed Lyman-alpha absorption that was seen during the transit of HD 209458b (ref. 2). They conclude that radiation pressure alone cannot explain the observations and that a peculiar stellar wind is needed. Here we show that radiation pressure alone can in fact produce the observed high-velocity hydrogen atoms. We also emphasize that even if the stellar wind is responsible for the observed hydrogen, to have a sufficient number of atoms for charge exchange with stellar wind, the energetic neutral atom (ENA) model also needs a significant escape from the planet atmosphere of similar amplitude as quoted in ref. 2.