Stellar dynamics |
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| Authors: | Ivan R King |
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| Institution: | 1. Berkeley Astronomy Dept., University of California, Calif., USA
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| Abstract: | This review attempts to place stellar dynamics in relation to other dynamical fields and to describe some of its important techniques and present-day problems. Stellar dynamics has some parallels, in increasing order of closeness, with celestial mechanics, statistical mechanics, kinetic theory, and plasma theory; but even in the last case the parallels are not very close. Stellar dynamics describes, usually through distribution functions, the motions of a large number of bodies as they all act on each other gravitationally. To a good approximation each star can be considered to move in the smoothed-out field of all the others, with random encounters between pairs of stars adding a slow statistical change to these smooth motions. Smooth-field dynamics has a well-developed theory, and the state of smooth stellar systems can be described in some detail. The ‘third integral’ presents an outstanding problem, however. Stellar encounters also have a well-developed theory, but close encounters and encounters of a single star with a binary pose serious problems for the statistical treatment. Star-cluster dynamics can be approached through a theory of smooth-field dynamics plus changes due to encounters, or alternatively through numerical simulations. The relation between the two methods is not yet close enough. The dynamical evolution of star clusters is still not fully understood. |
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