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Advances in Astronomy and Astrophysics, Volume 4 brings together numerous research works on different aspects of astronomy and astrophysics. This volume is composed of five chapters, and starts with a description of objective prism and its application in space observations. The next chapter deals with the possibilities of deriving reliable models of the figure, density distribution, and gravity field of the Moon based on data obtained through Earth-bound telescopes. These topics are followed by a discussion on the ideal partially relativistic, partially degenerate gas in an exact manner. A chapter examines first the effect of exchange of matter on the periods of close binary systems, and then briefly surveys the mechanisms of mass loss, other causes of period changes, and related evolutionary problems. The last chapter looks into the cometary origin of meteorites. This book will prove useful to astronomers and astrophysicists.