The young planet-mass object 2M1207b: A cool, cloudy, and methane-poor atmosphere

Travis S. Barman, Bruce MacIntosh, Quinn M. Konopacky, Christian Marois

Research output: Contribution to journalArticlepeer-review

116 Scopus citations


The properties of 2M1207b, a young (8Myr) planet-mass companion, have lacked a satisfactory explanation for some time. The combination of low luminosity, red near-IR colors, and L-type near-IR spectrum (previously consistent with T eff ∼ 1600 K) implies an abnormally small radius. Early explanations for the apparent underluminosity of 2M1207b invoked an edge-on disk or the remnant of a recent protoplanetary collision. The discovery of a second planet-mass object (HR8799b) with similar luminosity and colors as 2M1207b indicates that a third explanation, one of a purely atmospheric nature, is more likely. By including clouds, non-equilibrium chemistry, and low gravity, an atmosphere with effective temperature consistent with evolution cooling-track predictions is revealed. Consequently, 2M1207b, and others like it, requires no new physics to explain nor do they belong to a new class of objects. Instead they most likely represent the natural extension of cloudy substellar atmospheres down to low T eff and log (g). If this atmosphere only explanation for 2M1207b is correct, then very young planet-mass objects with near-IR spectra similar to field T dwarfs may be rare.

Original languageEnglish (US)
Article numberL39
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Jul 10 2011


  • brown dwarfs
  • planetary systems
  • stars: atmospheres

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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