CAREER: A Comprehensive Study of Proto--Planetary Nebulae Dust Shells and the Development of Experimental Astronomy Programs at the University of Illinois

职业：伊利诺伊大学原行星状星云尘埃壳的综合研究和实验天文学项目的开发

• 批准号: 9733697
• 负责人: Margaret Meixner
• 金额: $ 32万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-15 至 2005-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9733697&HistoricalAwards=false
• 关键词: CAREER; Comprehensive; Study; Proto; Planetary

9733697 Meixner Dr. Margaret Meixner, of the University of Illinois, is investigating proto-planetary nebulae dust shells around dying stars and developing experimental astronomy programs for graduate and undergraduate students. The research program, which focuses on the late stages of stellar evolution of intermediate mass stars (0.8 to 8 Solar masses), addresses two long standing problems in stellar astrophysics: What physical mechanism drives the asymptotic giant branch star mass loss? What is the nature of the circumstellar dust created by the asymptotic giant branch star during mass loss? The history of asymptotic giant branch star mass loss is imprinted in the circumstellar dustshells of proto-planetary nebulae (objects in transition between the stellar asymptotic giant branch and planetary nebula phases). To discern the final part of this history, Dr. Meixner is collecting infrared data on approximately 100 proto-planetary nebulae dustshells. Ground-based, mid-infrared (0.8-2.5 micrometers wavelength), images of these proto-planetary nebulae show the spatial distribution of the warm (about 300 degree K) dust in the inner regions. The spatial distribution of the scattered starlight is imaged in these proto-planetary nebulae using the Near-InfraRed IMager (NIRIM) on a laser-guided adaptive optics system. A computer program, which models the radiative transfer in the central star and dustshell system, will be used to quantitatively derive the 3D geometries of these dustshells and their inner radii. The information from the infrared data and Hubble Space Telescope images will be used in making the computer models. The 3D models of the geometries will provide insight into the geometry of mass loss during the star's final death throes. A preliminary investigation of several proto-planetary nebulae by Dr. Meixner et al showed that the geometries had an axial symmetry and this indicated that the star's loss mass at a higher rate in the equatorial plane than in the polar region. The data from the observations of the dustshell inner radii are used to estimate the dynamical ages for the proto-planetary nebulae. These ages will be used to test the theoretical timescales of stellar evolution predicted by other scientists. These theoretical timescales are uncertain because the mass loss processes which dominate this stage of stellar evolution are poorly understood. These data will be used to constrain the models of the characteristics of circumstellar dust, including the grain sizes, the composition, and the optical properties of the dust. The circumstellar dust created during the asymptotic giant branch mass loss process in stars is the single most important contribution to the dust observed in our Galaxy. The next generation of stars in our Galaxy are born from this dust enriched interstellar medium. Hence, the new understanding about this dust composition will improve our understanding of galactic evolution. Concurrent with this research program, two educational experimental astronomy programs are being developed. The infrared astronomy program will be expanded by involving graduate and undergraduate students in research on proto-planetary nebulae. These students will learn the latest in infrared observing techniques. A new introductory astronomy laboratory course, entitled Observing the Sky, will be created. This will be used for the large introductory courses that are populated by non-science majors. In this course, the students will learn about astronomical observations by doing observations in a supervised, small-group environment.

9733697伊利诺伊大学的Meixner Margaret Meixner博士正在调查垂死之星周围的原始星云尘埃壳，并为研究生和本科生开发实验性天文学计划。 该研究计划着重于中间质量恒星（0.8至8个太阳能）恒星演变的后期阶段，它解决了恒星天体物理学中两个长期存在的问题：哪些物理机制驱动渐近巨型分支星星恒星质量损失？ 在群众损失期间，渐近巨型分支恒星产生的双歧性灰尘的性质是什么？ 渐近巨型分支巨星质量损失的历史印在原始星云的偶尔粉尘壳（恒星渐近巨型分支与行星星云阶段之间的过渡中的物体中）。 为了辨别这一历史的最后一部分，Meixner博士正在收集大约100个原始星云的尘埃壳的红外数据。这些原始星际星云的图像显示了地面的中红外（0.8-2.5微米波长），显示内部区域中温暖（约300次K）灰尘的空间分布。 使用激光引导的自适应光学系统上的近红外成像仪（NIRIM）在这些原始星云中成像散射星光的空间分布。 将在中央恒星和防尘系统中建模辐射传递的计算机程序将用于定量得出这些尘埃壳及其内部半径的3D几何形状。 红外数据和哈勃太空望远镜图像中的信息将用于制作计算机模型。 几何模型的3D模型将洞悉恒星最终死亡术期间质量损失的几何形状。 Meixner等人博士对几个原始星际星云的初步研究表明，几何形状具有轴向对称性，这表明赤道平面的恒星损失质量比在极区域更高。 来自尘埃壳内部半径的观察结果的数据用于估计原始星际星云的动力学年龄。 这些年龄将用于测试其他科学家预测的恒星进化的理论时间表。 这些理论的时间尺度是不确定的，因为众所周知，众所周知，众所周知，众所周知。 这些数据将用于限制与灰尘的特性模型，包括谷物尺寸，成分和灰尘的光学特性。 恒星中渐近巨型分支质量损失过程中产生的脉冲灰尘是对我们星系中观察到的尘埃的最重要贡献。 我们银河系中的下一代恒星是从这种富含粉尘的星际介质中诞生的。 因此，对这种灰尘组成的新理解将改善我们对银河进化的理解。 与该研究计划同时，正在制定两个教育实验天文学计划。 红外天文学计划将通过让研究生和本科生参与原始星云研究来扩展。 这些学生将学习最新的红外观测技术。 将创建一个新的介绍性天文学实验室课程，标题为“观察天空”。 这将用于由非科学专业的大型入门课程。 在本课程中，学生将通过在有监督的小组环境中进行观察来了解天文观察。