Astronomers have found evidence that brown dwarf stars have their own weather. Results presented at the Jan. 8 meeting of the American Astronomical Society in Long Beach, Calif. have found patches and layers of material blown around in Earth-sized wind storms in the atmosphere of the brown dwarf 2MASSJ22282889-431026. NASA’s Spitzer and Hubble telescopes observed that the light given off by the dwarf varied as it rotated, and that the variations changed when observed with different wavelengths of light.
“What we see here is evidence for massive, organized cloud systems, perhaps akin to giant versions of the Great Red Spot on Jupiter,” said Adam Showman, a theorist at the University of Arizona. “These out-of-sync light variations provide a fingerprint of how the brown dwarf’s weather systems stack up vertically. The data suggest regions on the brown dwarf where the weather is cloudy and rich in silicate vapor deep in the atmosphere coincide with balmier, drier conditions at higher altitudes – and vice versa.”
A brown dwarf is sometimes referred to as a failed star. Lacking the mass to sustain hydrogen fusion, the dwarf will still radiate heat and light, but at lower levels than regular stars and will not be able to burn lithium, one of the characteristics that distinguishes a brown dwarf from a normal star. Some brown dwarfs, such as Gliese 229B, can be smaller than Jupiter.
The results have some researchers planning to look at many more nearby brown dwarfs to study their atmospheres.
"From studies such as this we will learn much about this important class of objects, whose mass falls between that of stars and Jupiter-sized planets," said Glenn Wahlgren, Spitzer program scientist at NASA Headquarters in Washington. "This technique will see extensive use when we are able to image individual exoplanets."
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