A global cloud map of the nearest known brown dwarf
A global cloud map of the nearest known brown dwarf
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DOI：
10.1038/nature12955
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发表时间：
2014-01-30
期刊：
影响因子：
64.8
通讯作者：
Kopytova, T.
中科院分区：
文献类型：
--
作者：
Crossfield, I. J. M.;Biller, B.;Kopytova, T.
褐矮星--质量比行星大，但质量不足以启动持续氢聚变为自发光恒星(1，2)提供动力的亚星体--出生时很热，随着年龄的增长慢慢变冷。当它们冷却到约2,300开尔文以下时，由铝酸钙、硅酸盐和铁组成的液体或晶体颗粒凝聚成大气中的“尘埃”(3，4)，在更低的温度(约1,300开尔文)(5，6)下消失。解释这种尘埃扩散的模型包括整个云层突然下沉到深不可测的大气中(5，7)，以及云层分裂成分散的小块(6，8)(如木星和土星(9)所示)。然而，到目前为止，对棕矮星的观测仅限于全球综合测量(10)，这可以揭示地表的不均匀，但不能明确地分辨地表特征(11)。在这里，我们报告了一张褐矮星表面的二维地图，它可以识别大范围的亮和暗特征，表明有斑驳的云。监测表明，全球天气模式演变的特征时间尺度约为一天。
Brown dwarfs-substellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars(1,2)-are born hot and slowly cool as they age. As they cool below about 2,300 kelvin, liquid or crystalline particles composed of calcium aluminates, silicates and iron condense into atmospheric 'dust'(3,4), which disappears at still cooler temperatures (around 1,300 kelvin)(5,6). Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unobservable atmosphere(5,7) and breakup of the cloud into scattered patches(6,8) (as seen on Jupiter and Saturn(9)). However, hitherto observations of brown dwarfs have been limited to globally integrated measurements(10), which can reveal surface inhomogeneities but cannot unambiguously resolve surface features(11). 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. Monitoring suggests that the characteristic timescale for the evolution of global weather patterns is approximately one day.