A patchy cloud model for the L to T dwarf transition

Mark S. Marley, Didier Saumon, Colin Goldblatt

Research output: Contribution to journalArticlepeer-review

142 Scopus citations


One mechanism suggested for the L to T dwarf spectral type transition is the appearance of relatively cloud-free regions across the disk of brown dwarfs as they cool. The existence of partly cloudy regions has been supported by evidence for variability in dwarfs in the late L to early T spectral range, but no self-consistent atmosphere models of such partly cloudy objects have yet been constructed. Here, we present a new approach for consistently modeling partly cloudy brown dwarfs and giant planets.We find that even a small fraction of cloud holes dramatically alter the atmospheric thermal profile, spectra, and photometric colors of a given object. With decreasing cloudiness objects briskly become bluer in J - K and brighten in J band, as is observed at the L/T transition. Model spectra of partly cloudy objects are similar to our models with globally homogenous, but thinner, clouds. Hence, spectra alone may not be sufficient to distinguish partial cloudiness although variability and polarization measurements are potential observational signatures. Finally, we note that partial cloud cover may be an alternative explanation for the blue L dwarfs.

Original languageEnglish (US)
Pages (from-to)L117-L121
JournalAstrophysical Journal Letters
Issue number1 PART 2
StatePublished - Nov 1 2010
Externally publishedYes


  • Brown dwarfs
  • Stars: atmospheres

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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