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Science 11 December 1998:
Vol. 282. no. 5396, p. 1953
DOI: 10.1126/science.282.5396.1953b
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This Week in Science
Brown dwarfs are caught in the middle: They are too massive to be planets and not massive enough to be stars. Gliese 229B was the first bona fide brown dwarf identified in 1995 and it remains the coldest brown dwarf (900 Kelvin) that has been studied. Griffith et al. (p. 2063) realized that Gliese 229B was too warm to have ice clouds like Jupiter, and too cool to have silicate-rich clouds like some stars. This lack of clouds allowed them to observe Gliese 229B's atmosphere with near-infrared wavelength spectroscopy with the Keck I Telescope. The spectrum suggests the presence of an organic-rich haze in Gliese 229B's atmosphere that probably formed as a result of incident radiation from its primary star, just like the mechanism suggested for the formation of Jupiter's stratosphere. Thus the radiation from a star may cause a brown dwarf to become more planet-like.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
