While the atmosphere consists of only a tiny fraction of the overall stellar radius and mass (respectively about 10 − 3 and 10 − 12 ), it represents a crucial boundary layer between the dense interior and the near vacuum outside, from which the light we see is released, imprint- ing it with detailed spectral signatures that, if properly interpreted in terms of the physics principles coupling gas and radiation, provides essential information on stellar 特性。尤其是,光谱线的身份,优势和形状(或轮廓)包含具有大气实际状态的重要线索,例如化学成分,电离状态,有效温度,表面重力,旋转速率。但是,必须根据详细的模型气氛正确解释这些这些,该模型气氛适当地说明了基本的物理过程,即:原子的激发和电离;辐射的相关吸收,散射和发射及其对光子能量或频率的依赖;最后,这如何导致发射通量与频率的这种复杂变化,从而使观察到的光谱构成了特征。这种模型大气的解释恒星光谱构成了推断质量,半径和光度等基本恒星特性的基础。
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