Nebular Hydrodynamical Evolution

行星状星云(PN)是环绕在致密而炽热的中心恒星周围的形状各异的气态外壳。它们是由发光的、高度进化的红巨星产生的强烈恒星风形成的。这种物质抛射过程夺走了恒星外部富含氢的包层，留下了主要由氦和更重元素组成的致密恒星。当它们富含氢的包层被抛出并初步形成Pn时，来自中央恒星的高速风塑造了星云，并影响了它们的运动学和热力学性质。首席调查员(PI)建议继续他们目前由国家科学基金会资助的关于PN的空间和运动学性质的研究。他们将构建一个二维流体力学计算机代码，并辅之以碰撞、光子加热和辐射冷却算法。PI计划将这个代码应用于Pn及其光晕演化中的激波和碰撞过程，恒星风的历史，以及嵌入在一些Pn中的非常低电离的特殊结和边缘的起源。将与Pn的观测数据进行详细的比较。

Planetary nebulae (PN) are gaseous shells of varying shapes surrounding compact, hot central stars. They are formed by intense stellar winds from luminous, highly evolved red giant stars. This process of mass ejection robs the stars of their outer hydrogen- rich envelopes, leaving behind compact stars consisting predominantly of helium and heavier elements. Upon ejection of their hydrogen-rich envelopes and the initial formation of the PN, high-speed winds from the central stars shape the nebulae and affect their kinematic and thermodynamic properties. The Principal Investigators (PIs) propose to continue with their current NSF-funded study of the spatial and kinematic nature of PN. They will construct a two-dimensional hydrodynamic computer code, supplemented with collisional and photon heating and radiative cooling algorithms. The PIs plan to apply this code to shocks and collisional processes in the evolution of PN and their halos, the history of stellar winds, and the origin of the peculiar knots and rims of very low ionization embedded in some PN. Detailed comparisons with observational data of PN will be made.