THE YOUNG PLANET-MASS OBJECT 2M1207b: A COOL, CLOUDY, AND METHANE-POOR ATMOSPHERE
- Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001 (United States)
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)
- National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)
The properties of 2M1207b, a young ({approx}8 Myr) 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{sub eff} {approx} 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{sub 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.
- OSTI ID:
- 21562543
- Journal Information:
- Astrophysical Journal Letters, Vol. 735, Issue 2; Other Information: DOI: 10.1088/2041-8205/735/2/L39; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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