The Dusty Atmosphere of the Brown Dwarf Gliese 229B
Caitlin A. Griffith,
Roger V. Yelle,
Mark
S. Marley
The brown dwarf Gliese 229B has an observable atmosphere too warm
to contain ice clouds like those on Jupiter and too cool to contain
silicate clouds like those on low-mass stars. These unique conditions
permit visibility to higher pressures than possible in cool stars or
planets. Gliese 229B's 0.85- to 1.0-micrometer spectrum indicates
particulates deep in the atmosphere (10 to 50 bars) having optical
properties of neither ice nor silicates. Their reddish color suggests
an organic composition characteristic of aerosols in planetary
stratospheres. The particles' mass fraction (10
7) agrees with a photochemical origin
caused by incident radiation from the primary star and suggests the
occurrence of processes native to planetary stratospheres.
C. A. Griffith, Department of Physics and Astronomy, Northern
Arizona University, Flagstaff, AZ 86011-6010, USA. R. V. Yelle, Center for Space Physics, Boston University, 725 Commonwealth
Avenue, Boston, MA 02215, USA. M. S. Marley, Department of
Astronomy, New Mexico State University, Las Cruces, NM 88003-0001,
USA.
