U.S.-Netherlands Cooperative Research on Hydrodynamic Modelsof the Shaping of Planetary Nebulae

该奖项将使华盛顿大学的布鲁斯·巴利克教授能够与荷兰莱顿大学的文森特·艾克教授合作，对行星状星云进行研究。行星状星云是与恒星生命的最后阶段有关的高温电离气体云。他们的合作将包括改进行星状星云的观测描述，开发改进的模型来解释星云复杂而对称的形状的原因。Balick教授有一个关于行星状星云的广泛的观测数据库，他在通过详细的观测来检验模型预测方面有经验。Icke教授是理论星云流体动力学方面的专家，他开发了一个非常复杂的计算机模拟程序，该程序已成功地用于模拟其他恒星物体，如超新星残骸。与Balick博士的合作将有助于使用美国的超级计算机来运行模拟星云动力学所需的复杂程序。行星状星云是由老化的恒星喷出的气体外壳。喷射被认为发生在两个阶段，首先是一个相当缓慢的“风”，包含恒星的外层（在数千年的时间里），然后在几个世纪内更快地驱逐更深的层。理论模型和最近的观测表明，当这股快速的风超越并与早期喷射的外层相互作用时，星云获得了它们的形状。最近一项对50个行星状星云的调查显示，风形成的概念总体上是有效的，但是用来解释这一现象的模型过于简单。这个项目的目标是开发和测试更复杂的模型来解释行星状星云的形状和演化。三维流体动力学模型需要数年的时间来开发，并且只能在超级计算机的帮助下进行合理的测试。Balick博士的观测数据和模型测试技能，以及Icke博士的理论见解和修改他已经开发的计算机代码的能力，将极大地促进解释星云形状所需的增强模型的发展。最终，他们的合作将有助于解决一些长期存在的关于行星状星云的形状和演化的问题。

This award will enable Professor Bruce Balick of the University of Washington to collaborate with Professor Vincent Icke of the University of Leiden, The Netherlands, in a study of planetary nebulae, which are hot, ionized clouds of gas associated with the final stages of stellar life. Their collaboration will involve obtaining improved observational descriptions of planetary nebulae and developing improved models to explain the causes of the intricate and symmetrical shapes of the nebulae. Professor Balick has an extensive observational data base on planetary nebulae and he has experience in testing model predictions by detailed observations. Professor Icke is an expert in theoretical nebular hydrodynamics, and has developed a very sophisticated computer simulation program that has been successfully adapted for modelling other stellar objects such as supernovae remnants. Collaboration with Dr. Balick will facilitate access to a U.S. supercomputer to run the complex programs needed to model nebular dynamics. Planetary nebulae are gaseous shells ejected by aging stars. The ejection is thought to occur in two stages, first as a rather slow "wind" containing the outer layers of the star (over a period of thousands of years), then a much faster expulsion of deeper layers in only a few centuries. Theoretical models and recent observations suggest that the nebulae acquire their shapes as this fast wind overtakes and interacts with the outer layers ejected earlier. A recent survey of 50 planetary nebulae shows that the concept of wind shaping is generally valid, but that the models developed to explain the phenomenon are much too simplistic. The goal of this project is to develop and test more complex models to explain the shapes and evolutions of planetary nebulae. Three-dimensional hydrodynamic models require years to develop and can only reasonably be tested with the aid of a supercomputer. Development of the enhanced models needed to explain nebular shapes will be greatly facilitated by the combination of Dr. Balick's observational data and model testing skills with Dr. Icke's theoretical insights and ability to modify the computer code he has already developed. Ultimately, their collaboration should contribute to resolving some longstanding questions about the shapes and evolution of planetary nebulae.