This book is addressed to a readership of beginning graduate students and up. In contrast with other monographs on related subjects, it emphasizes some physical and methodological aspects. Two distinctive features are the emphasis on the similarities between the dynamics of stellar systems and the collective behavior of electromagnetic plasmas and the focus on a few important dynamical issues that are raised by observations. In the adopted semiempirical approach, the study of dynamics thus develops under the guidance and inspiration of empirical facts. Therefore, the book, although rich in quantitative analysis, reduces the mathematical discussion to its essentials. The level of presentation is not excessively technical. There is no intention to give a full account of all aspects (many of which are of fundamental importance) of interest in this broad research area; the reader is referred to the many authoritative books already available. Instead, this book tries to capture a lively synthesis to arouse curiosity in a reader who is not already professionally involved in this area of celestial physics.

From the methodological point of view, the book focuses on the general use of asymptotic methods, and it gives in detail the mathematical structure of some derivations when they may be useful for more general purposes. Asymptotic methods are flexible tools to obtain approximate solutions that give priority to the richness of ingredients in a physical problem; technically speaking, these methods recognize the importance of singular perturbations in the realization of physical processes.