Die Dichtewellentheorie der Spiralstruktur. Erfolge und offene Probleme

One of the principal subjects of study of dynamical astronomy in the second half of the twentieth century is related to the spatial characteristics of the spiral structure in the Galaxy and the factors involved in maintaining the structure in the presence of pronounced differential galactic rotation. The density wave theory first considered by Lin and Shu (1964) has provided a useful basis for the investigation of this subject. Although it has not been possible to answer all questions, it can be said that the density wave theory has made important contributions to astronomical research, because the conclusions based on this theory have been of value also for many other study areas of astronomy. The basic concepts of the density wave theory are discussed along with its most important applications.