High-temperature photochemistry in the atmosphere of HD 189733b

M. R. Line, M. C. Liang, Y. L. Yung

Research output: Contribution to journalArticlepeer-review

90 Scopus citations


Recent infrared spectroscopy of hot exoplanets is beginning to reveal their atmospheric composition. Deep within the planetary atmosphere, the composition is controlled by thermochemical equilibrium. Photochemistry becomes important higher in the atmosphere, at levels above ∼1 bar. These two chemistries compete between 1 and 10 bars in hot-Jupiter-like atmospheres, depending on the strength of the eddy mixing and temperature. HD189733b provides an excellent laboratory in which to study the consequences of chemistry of hot atmospheres. The recent spectra of HD189733b contain signatures of CH4, CO 2, CO, and H2O. Here we identify the primary chemical pathways that govern the abundances of CH4, CO2, CO, and H2O in the cases of thermochemical equilibrium chemistry, photochemistry, and their combination. Our results suggest that the disequilibrium mechanisms can significantly enhance the abundances of these species above their thermochemical equilibrium value, so some caution must be taken when assuming that an atmosphere is in strict thermochemical equilibrium.

Original languageEnglish (US)
Pages (from-to)496-502
Number of pages7
JournalAstrophysical Journal
Issue number1
StatePublished - 2010
Externally publishedYes


  • Atmospheric effects
  • Methods: numerical
  • Planetary systems
  • Planets and satellites: atmospheres
  • Radiative transfer
  • Stars: individual (HD 189733b)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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