Active Galactic Nuclei

Starting with this volume, the Lecture Notes of the Advanced Courses of the Swiss Society for Astrophysics and Astronomy will be published annually. In each course, three lectures given by specialists in their respective fields cover different aspects of the subject. This course, the 20th, held at Les Diablerets in April 1990, dealt with current research on active galactic nuclei; it represents current views on the subject. The previous courses considered a wide variety of subjects, beginning with "Theory of Stellar Athmospheres" in 1971 and ending with "The Milky Way as a Galaxy" in 1989. The lecture notes of these Saas-Fee courses have appeared previously as publications of the Geneva Observatory.