Collaborative Research: An integrated experimental and observational study of cosmic silicate astromineralogy

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。硅酸盐尘埃是许多天体物理环境的重要组成部分。由于“无定形”硅酸盐的光谱特征已经在不同的环境中被观察到，从我们的太阳系和彗星的大气层，到垂死恒星的星周喷射物，再到活动星系核的环境。尘埃在恒星形成过程中起着至关重要的作用，并有助于星际过程的几个方面，如气体加热和分子的形成。由于演化恒星的质量损失是由辐射驱动的，因此它与星周尘埃的精确性质密切相关。然而，组成和结构对尘埃光谱的影响却没有得到很好的约束，导致解释上的模糊性。该项目将研究“无定形”硅酸盐矿物的实验室红外光谱和玻璃化转变温度，为约束尘埃模型提供必要的光谱和物理性质数据。这些数据将使我们更好地了解各种硅酸盐形成和在许多天体物理环境中被处理的条件，包括各种质量的垂死恒星，年轻的恒星物体和星际介质。一系列的实验室研究将探索具有良好特征的辉石和千英石的光谱特征的变化，包括固溶行为和铁氧化态的变化。一个关键的结果将是确定是否晶粒类型，如玻璃，多晶样品，玻璃-晶体混合物，实际上可以区分光谱。这项工作将提供硅酸盐玻璃和熔体的物理数据，如玻璃转变温度和热容量，使人们更好地了解各种硅酸盐形成和加工的条件，以及瞬态加热事件的影响。这些结果将用于研究渐近巨星分支和红超巨星喷出物的矿物学，深入了解相互竞争的尘埃形成机制，并通过测试它们是玻璃状还是多晶状来找到星际硅酸盐的形成位置。这是一项跨学科研究，涉及一位天体物理学家、一位矿物物理学家和一位实验岩石学家。收集的数据对于研究硅酸盐熔体很重要，因为硅酸盐熔体与类地行星上的岩浆活动有关，而对玻璃工业的研究意义也不小。思想和技术的相互交融为参与的研究生提供了广泛的跨学科教育，拓展了视野，促进了思维的突破。女性pi（一个代表性不足的群体）是这些领域女性的强大榜样，也是年轻研究人员的积极导师。

AST-0908302/0908309 Speck/Hofmeister This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Silicate dust is an important component of many astrophysical environments. Spectral features due to "amorphous" silicates have been observed in diverse settings ranging from our solar system and the atmospheres of comets, to the circumstellar ejecta of dying stars, to the environments of active galactic nuclei. Dust plays an essential role in star formation processes, and contributes to several aspects of interstellar processes such as gas heating and the formation of molecules. Since mass-loss from evolved stars is radiation driven, it is intimately linked to the precise nature of the circumstellar dust. However, the effects of composition and structure on the spectra from dust are poorly constrained, leading to ambiguities in interpretation. This project will investigate the laboratory infrared spectra and glass transition temperatures of "amorphous" silicate minerals, providing the necessary spectral and physical property data to constrain dust models. These data will allow a better understanding of the conditions under which various silicates form and are processed in many astrophysical environments, including dying stars of all masses, young stellar objects, and the interstellar medium. A series of laboratory investigations will explore the variation in spectral signatures of well-characterized suites of pyroxenes and melilites, including changes due to solid-solution behavior and variable iron oxidation state. A key outcome will be to determine whether grain types such as glasses, polycrystalline samples, and glass-crystallite mixtures, can in fact be distinguished spectroscopically. The work will provide physical data for silicate glasses and melts, such as glass transition temperature and heat capacity, giving a better understanding of the conditions under which various silicates form and are processed, and the effect of transient heating events. The results will then be used to study the mineralogy of the ejecta of asymptotic giant branch and red supergiant stars, gaining insight into competing dust formation mechanisms, and to find the formation sites of interstellar silicates by testing whether they are glassy or poly-crystalline. This is a cross-disciplinary study involving an astrophysicist, a mineral physicist and an experimental petrologist. The data to be collected are important for studies of silicate melts, which pertain to magmatism on terrestrial planets, and not insignificantly to the glass industry. The cross-fertilization of ideas and techniques provides a broad, interdisciplinary education for the involved graduate students, expanding horizons and promoting thinking outside the box. The female PIs (an under-represented group) are strong role models for women in these fields, and active mentors to younger researchers.