恒星大气中的天气：仙女座α星水星云的动力学
Weather in stellar atmosphere: the dynamics of mercury clouds in alpha Andromedae
摘要：
在恒星表面形成持久结构通常归因于强磁场的作用。这一范例得到了太阳和活跃的晚型恒星中不断演变的冷点以及早期型磁星中静止化学点的观测结果的支持。然而，我们对非磁性早期型恒星仙女座α中的汞斑进行了七年的监测，结果表明，磁驱动结构形成的图片基本上是不完整的。使用间接恒星表面映射技术，我们构建了一系列的2-D图像的恒星，并发现在这颗恒星的水星云盖的长期演变。这是第一次在任何恒星中观察到的显着结构形成过程，可以归因于原子扩散产生的重元素云的非平衡动态演化，并且可能具有与类地行星和巨行星上的天气模式相同的基本物理学。
英文摘要：
The formation of long-lasting structures at the surfaces of stars is commonly ascribed to the action of strong magnetic fields. This paradigm is supported by observations of evolving cool spots in the Sun and active late-type stars, and stationary chemical spots in the early-type magnetic stars. However, results of our seven-year monitoring of mercury spots in non-magnetic early-type star alpha Andromedae show that the picture of magnetically-driven structure formation is fundamentally incomplete. Using an indirect stellar surface mapping technique, we construct a series of 2-D images of starspots and discover a secular evolution of the mercury cloud cover in this star. This remarkable structure formation process, observed for the first time in any star, is plausibly attributed to a non-equilibrium, dynamical evolution of the heavy-element clouds created by atomic diffusion and may have the same underlying physics as the weather patterns on terrestrial and giant planets.
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