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

这一奖项将使华盛顿大学的布鲁斯·巴里克教授能够与荷兰莱顿大学的文森特·艾克教授合作研究行星星云，行星星云是与恒星生命最后阶段相关的炽热、电离的气体云。他们的合作将包括改进对行星状星云的观测描述，并开发改进的模型来解释星云复杂和对称形状的原因。巴里克教授拥有丰富的行星状星云观测数据库，他有通过详细观测来检验模型预测的经验。Icke教授是理论星云流体力学方面的专家，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，如超新星遗迹。与巴里克博士的合作将有助于获得一台美国超级计算机，以运行建立星云动力学模型所需的复杂程序。行星状星云是由年老的恒星抛出的气态外壳。抛射被认为分两个阶段发生，第一个阶段是相当缓慢的“风”，包含恒星的外层(历经数千年)，然后在短短几个世纪内以更快的速度排出更深的层。理论模型和最近的观测表明，当这种快速风赶上并与较早喷出的外层相互作用时，星云就会形成自己的形状。最近对50个行星状星云的调查表明，风形成的概念总体上是有效的，但为解释这一现象而开发的模型过于简单化。该项目的目标是开发和测试更复杂的模型，以解释行星状星云的形状和演化。三维流体力学模型的开发需要数年时间，而且只有在超级计算机的帮助下才能进行合理的测试。巴里克博士的观测数据和模型测试技能与艾克博士的理论见解和修改他已经开发的计算机代码的能力相结合，将极大地促进解释星云形状所需的增强模型的开发。最终，他们的合作应该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.