Evaporation of the planet HD  189733b observed in H i Lyman-α

A. Lecavelier Des Etangs, D. Ehrenreich, A. Vidal-Madjar, G. E. Ballester, J. M. Désert, R. Ferlet, G. Hébrard, D. K. Sing, K. O. Tchakoumegni, S. Udry

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267 Scopus citations


We observed three transits of the extrasolar planet HD  189733b in H i Lyman-α and in a few other lines in the ultraviolet with HST/ACS, in the search for atmospheric signatures. We detect a transit signature in the Lyman-α light curve with a transit depth of 5.05 ± 0.75%. This depth exceeds the occultation depth produced by the planetary disk alone at the 3.5σ level (statistical). Other stellar emission lines are less bright, and, taken individually, they do not show the transit signature, while the whole spectra redward of the Lyman-α line has enough photons to show a transit signature consistent with the absorption by the planetary disk alone. The transit depth's upper limits in the emission lines are 11.1% for O i λ1305 à   and 5.5% for C ii λ1335 à   lines.â€

Original languageEnglish (US)
Article numberA72
JournalAstronomy and astrophysics
Issue number10
StatePublished - May 21 2010


  • Planetary systems
  • Stars: individual: HD 189733

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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