On April 28 1986 Cornelis de Jager reached the age of 65 years. On April 30 he officially retired from the University of Utrecht where he has held a Chair for Stellar Astrophysics, later changed into Space Physics, since 1958. Cees de Jager, as he prefers to be called by his friends, has had an active and successful life in science. His interest in astronomy was raised by his father under the clear skies of Celebes (Indonesia). He started a study in physics and astronomy as a student of the late M. Minnaert in Utrecht during World War II. When in 1943 the occupying forces recruited students who did not want to sign the declaration of loyalty for their war-efforts, Cees and three fellow students went into hiding at the Observatory in Utrecht. During this very "quiet" period van de Hulst developed the theory of the 21 em radiation of neutral hydrogen and de Jager started the observations of variable stars in the pitch dark nights of a country at war. The study of Beta Cepheids rapid ly awoke his interest which was kept throughout the years. In 1958 he organized an international campaign to observe 12 Lac spectroscopically and photometrically, which was a great success."

A strange field of speculation is opened by this phenomenon ... here we have a star fitfully variable to an astonishing extent. and whose fluctuations are spread over centuries. apparently in no settled period. and with no regularity of progression. What origin can we ascribe to these sudden flashes and relapses? What conclusions are we to draw as to the comfort or habitability of a system depending for its supply of light and heat on so uncertain a source? -- J. F. W. Herschel We can imagine, at least, that the study of Luminous Blue Variable stars began as the official court astrophysicists of Eridu speculated about a new 5000 years ago first-magnitude star which persisted in their southern sky for several years.2 After that the topic languished for a while, but now it has been renewed following recent observations by Blaeu (P Cygni, c.1600) and Herschel (1] Argus, c.1840) ... -- More soberly, it is only within the past few years that we have begun to understand LBV's and to recognize their coherence as a class. Thus only a minority of astronomers are familiar yet with this relatively new topic, whose potential impli cations are of great interest (see below). One purpose of this book, we hope, will be to provide an accessible overview of the subject for interested astronomers and astrophysicists in general."

Planetary nebulae present a fascinating range of shapes and morphologies. They are ideal laboratories for the study of different astrophysical processes: atomic physics, radiative transfer, stellar winds, shocks, wind-wind interaction, and the interaction between stellar winds and the interstellar medium. In addition, planetary nebulae provide information about the late stages of stellar evolution. In the last five years studies of planetary nebulae have progressed very rapidly and new phenomena and insights have been gained. This is partly due to new observations (e.g. from the Hubble Space Telescope, the ISO satellite and new infrared and millimeter spectrographs) and partly to the advancement of hydrodynamic simulations of the structures of planetary nebulae (PN). Many of these new results were reported at IAU Symposium 180 in Groningen, the Netherlands, on August 26 to 30, 1996. This symposium was dedicated to one of the pioneers of PN research: Stuart Pottasch. These proceedings contain chapters on: Introduction to PN with the basic parameters Distances of PN The central stars of PN The envelopes of PN The evolution from AGB to PN The evolution from PN to white dwarfs PN in the galactic context PN in extragalactic systems The future of PN research . The book contains 29 reviews and more than 200 shorter contributions.

Planetary nebulae present a fascinating range of shapes and morphologies. They are ideal laboratories for the study of different astrophysical processes: atomic physics, radiative transfer, stellar winds, shocks, wind-wind interaction, and the interaction between stellar winds and the interstellar medium. In addition, planetary nebulae provide information about the late stages of stellar evolution. In the last five years studies of planetary nebulae have progressed very rapidly and new phenomena and insights have been gained. This is partly due to new observations (e.g. from the Hubble Space Telescope, the ISO satellite and new infrared and millimeter spectrographs) and partly to the advancement of hydrodynamic simulations of the structures of planetary nebulae (PN). Many of these new results were reported at IAU Symposium 180 in Groningen, the Netherlands, on August 26 to 30, 1996. This symposium was dedicated to one of the pioneers of PN research: Stuart Pottasch. These proceedings contain chapters on: Introduction to PN with the basic parameters Distances of PN The central stars of PN The envelopes of PN The evolution from AGB to PN The evolution from PN to white dwarfs PN in the galactic context PN in extragalactic systems The future of PN research . The book contains 29 reviews and more than 200 shorter contributions.

This long-awaited graduate textbook, written by two pioneers of the field, is the first to provide a comprehensive introduction to the observations, theories and consequences of stellar winds. The rates of mass loss and the wind velocities are explained from basic physical principles. This book also includes chapters clearly explaining the formation and evolution of interstellar bubbles, and the effects of mass loss on the evolution of high- and low-mass stars. Each topic is introduced simply to explain the basic processes and then developed to provide a solid foundation for understanding current research. This authoritative textbook is designed for advanced undergraduate and graduate students and researchers seeking an understanding of stellar winds and, more generally, supersonic flows from astrophysical objects. It is based on courses taught in Europe and the US over the past twenty years and includes seventy problems (with answers) for coursework or self-study.

This long-awaited graduate textbook, written by two pioneers in the field, provides a comprehensive introduction to the observations, theories, and consequences of stellar winds. The rates of mass loss and the wind velocities are explained from basic physical principles. This textbook also includes chapters clearly explaining the formation and evolution of interstellar bubbles and the effects of mass loss on the evolution of high- and low-mass stars. Each topic is introduced simply to explain the basic processes and then developed to provide a solid foundation for understanding current research. This authoritative textbook is designed for advanced undergraduate and graduate students and researchers seeking an understanding of stellar winds and, more generally, supersonic flows from astrophysical objects. It is based on courses taught in Europe and the United States over the past twenty years and includes seventy problems for coursework or self-study.