The Physical and Chemical Properties of Circumstellar Matter

当前天文学研究的一个重要领域是研究红巨星在“行星状星云”阶段演化为白矮星时的质量损失。虽然这项研究本身对理解恒星演化具有重要意义，但它也很重要，因为行星状星云很亮，可能相对容易观察。因此，行星状星云是研究“星周物质”特性的特别方便的对象，“星周物质”是最近从热恒星喷射出来的密度介于恒星和星际气体物质之间的物质。处于类似状态的物质也会因为不同的原因出现在恒星周围，特别是在相互作用的双星、b发射星和密集的分子星际云周围的“盘”。然而，在这些环境中，通常很难观察到这种气体并诊断其性质。首席研究员（PI）建议继续之前nsf支持的物质物理和化学性质的研究，因为它在密集的“风”中离开恒星，最终与周围的星际气体混合。PI将测定原子、分子和辐射（星光）之间的反应速率，以了解物质形式（离子、中性原子和分子）的分布。因为这些原子会辐射出它们从气体运动中吸收的热能，这一知识将使我们了解与恒星不同距离处物质的温度和密度。然后可以将这些理论预测与无线电（毫米波长）阵列的新观测结果进行比较。然后将评估模型的正确性。

An important area of current astronomical research concerns the study of mass loss of red giant stars as they evolve to white dwarfs through the "planetary nebula" stage. Although this research is significant to an understanding of stellar evolution in its own right, it is also important because planetary nebulae are bright and may be observed comparatively easily. Thus, planetary nebulae are particularly convenient objects to study to learn the properties of "circumstellar matter", material which has has been recently ejected from hot stars in densities intermediate between stellar and interstellar gas material. Matter in a similar state also occurs around stars for different reasons, in particular as "disks" around interacting binary stars, B-emission stars, and dense molecular interstellar clouds. However, in these environments it is often difficult to observe this gas and to diagnose its properties. The Principal Investigator (PI) proposes to continue previous NSF-supported research on the physical and chemical properties of matter as it leaves the star in a dense "wind" and eventually mingles with ambient interstellar gas. The PI will determine reaction rates among atoms, molecules, and radiation (starlight) in order to understand the distribution of forms of matter (ions, neutral atoms, and molecules). Because these atoms radiate away thermal energy that they absorb from gas motions, this knowledge will lead to an understanding of the temperature and density of matter at different distances from the star. Comparisons of these theoretical predictions can then be made with new observations from radio (millimeter wavelength) arrays. The correctness of the models will then be evaluated.