Wednesday, January 29, 2014

First Global Cloud Map of Luhman 16B

A Global Cloud Map of the Nearest Known Brown Dwarf


Crossfield et al


Brown dwarfs – interstellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars – are born hot and slowly cool as they age. As they cool below ~2300 K, liquid or crystalline particles composed of calcium aluminates, silicates, and/or iron condense into atmospheric “dust” which disappears at still cooler temperatures (~1300 K). Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unobservable atmosphere or breakup of the cloud into scattered patches (as seen on Jupiter and Saturn), but to date observations of brown dwarfs have been limited to globally integrated measurements; such measurements can reveal surface inhomogeneities but cannot unambiguously resolve surface features11. Here we report a two dimensional map of a brown dwarf's surface that allows identification of large-scale bright and dark features, indicative of patchy clouds.

Geographic localization of such features, and the ability to create timelapsed extrasolar weather movies in the near future, provide important new constraints on the formation, evolution, and dispersal of clouds in brown dwarf and extrasolar planet atmospheres.

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