In this IAU Symposium on Wolf--Rayet stars, binary aspects received ample attention, notably because of the recognition that many observations of spectral and photometric variability at all accessible wavelengths are related to colliding winds or other forms of wind interaction. The basic structure of the conference and its proceedings is basic parameters and general properties of WR stars; state of the art model atmospheres for WR stars, anisotropic mass loss and disk formation of WR stars, properties of WR binaries; influence of stellar winds on mass transfer in hot massive binary evolution; dust formation near WR stars and other circumstellar phenomena; and hydrodynamics and high-energy physics of colliding winds in WR+O binaries and of WR winds interacting with compact objects. Within this framework 20 invited reviews, 38 invited oral contributions, and 76 poster papers were presented at the Symposium, entertaining 111 astronomers from 24 countries. These proceedings provide up-to-date information on all aspects of Wolf--Rayet atmospheres, binaries, and colliding winds.

SHORTLISTED FOR THE ROYAL SOCIETY SCIENCE BOOK PRIZE 2021 FINALIST FOR THE PEN/E.O. WILSON LITERARY SCIENCE WRITING AWARD AN AMAZON BEST BOOK OF 2020 To be an astronomer is to journey to some of the most inaccessible parts of the globe, braving mountain passes, sub-zero temperatures, and hostile flora and fauna. Not to mention the stress of handling equipment worth millions. It is a life of unique delights and absurdities ... and one that may be drawing to a close. Since Galileo first pointed his telescope at the heavens, astronomy has stood as a fount of human creativity and discovery, but soon it will be the robots gazing at the sky while we are left to sift through the data. In The Last Stargazers, Emily Levesque reveals the hidden world of the professional astronomer. She celebrates an era of ingenuity and curiosity, and asks us to think twice before we cast aside our sense of wonder at the universe.

It is a pleasure to present this work, which has been well received in German-speaking countries through four editions, to the English-speaking reader. We feel that this is a unique publication in that it contains valuable material that cannot easily-if at all-be found elsewhere. We are grateful to the authors for reading through the English version of the text, and for responding promptly (for the most part) to our queries. Several authors have supplied us, on their own initiative or at our suggestion, with revised and updated manuscripts and with supplementary English references. We have striven to achieve a translation of Handbuch fUr Sternfreunde which accurately presents the qualitative and quantitative scientific principles con tained within each chapter while maintaining the flavor of the original Ger man text. Where appropriate, we have inserted footnotes to clarify material which may have a different meaning and/or application in English-speaking countries from that in Germany. When the first English edition of this work, Astronomy: A Handbook (translated by the late A. Beer), appeared in 1975, it contained 21 chapters. This new edition is over twice the length and contains 28 authored chap ters in three volumes. At Springer's request, we have devised a new title, Compendium of Practical Astronomy, to more accurately reflect the broad spectrum of topics and the vast body of information contained within these pages."

In this Symposium, researchers specializing in pulsation, rotation, magnetic fields and stellar winds are brought together for the first time in order to broaden our understanding of O and B stars. Thanks to advances in digital spectroscopy, new types of pulsating B stars have been discovered. The pulsations can be understood in terms of the recent revision of metal opacities, but the effects of rapid rotation and magnetic fields need further study. Observations in the UV and X-ray regions demonstrate that many B and Be stars show other activity, besides pulsation which is not yet understood. The reason for the enhanced mass loss in Be stars is a question which dominates the Symposium and which remains unanswered, although it is surely to be found in activity at or near the photosphere coupled with rotation. It is shown that the geometry of the circumstellar envelopes around Be stars is indeed a flattened disk as they can now be optically resolved. The variability of radiatively-driven winds from O and B stars are likely related to the rotation of the star. This underlines the central theme of the book: that the various phenomena seen in these stars cannot be studied in isolation.

Spacecraft have explored the interplanetary medium between the orbits of Mercury and Pluto, revealing the exotic and beautiful nature of the environment of our planet and sun. This book summarizes the principle results of these historic expeditions. Magnetohydrodynamics provides the framework for interpreting the observations, and the observations have greatly enriched the subject of magnetohydrodynamics. Numerous figures in the book illustrate the essential observations and fundamental concepts. Simple equations summarize basic physical and phenomenological relations observed in the interplanetary medium. Fundamental objects observed in the interplanetary medium include various types of MHD shocks, tangenital and rotational discontinuities, and force-free field configurations. Fundamental processes observed in the interplanetary medium include the interaction among shocks (which can be classified using catastrophic theory), the formation of merged interaction region regions associated with various types of flows, the destruction of flows, the growth of the Kelvin-Helmholtz instability and formation of a heliospheric vortex street, the development of multifractal fluctuations on various scales, and the evolution of multifractal intermittent turbulence. These physical objects and processes are of fundamental interest in themselves. The knowledge about them derived from interplanetary investigations has applications to magnetospheric physics, solar physics, cosmic ray physics and astrophysics. The book contains an extensive set of reference that gives the readers access to the detailed results in the literature.

Active Galactic Nuclei radiate over the electro-magnetic spectrum from radio waves to gamma rays. Understanding the physics of these objects therefore requires the synthesis of results from many different domains of Astronomy. It was the aim of the conference "Active Galactic Nuclei across the Electromagnetic Spectrum" to provide a forum where this exchange could take place. Some 300 astronomers participated to the conference, 250 of them presented results either as oral papers or in the form of posters. Observations in all domains of the electro magnetic spectrum in which astronomical observations can be made from the ground or from space were presented. Many theoretical contributions were also given. There has been a tremendous growth in the number and quality of Astronomical obser vations in many spectral domains over the past several years. Students of Active Galactic Nuclei have been particularly keen to make use of the available facilities (both space born and on the ground), often in a very organised way, in order to obtain repeated simultane ous data covering large bands of the spectrum. This approach has produced a qualitatively new set of data for understanding the physics of Active Galactic Nuclei. The task of the meeting was to review this data in a coherent way."

The concept of Stellar Populations has played a fundamental role in astronomy in the last few decades. It was introduced by Walter Baade after he was able to resolve the Andromeda Nebula and its companions into stars when he used red-sensitive plates and realised that there were two fundamentally different Herzsprung-Russell diagrams in our and these nearby galaxies (common stars in the solar neighborhood versus globular clusters). This result was published in two papers in 1944 in volume 100 of the Astrophysical Journal. Subsequent research gave the concept a much firmer basis and at the famous Vatican Symposium of 1957 resulted in a general scheme of the concept and a working hypothesis for idea's on the formation and evolution of the Galaxy. This has been a guiding principle of studies of our and other galaxies for decades. Some years ago it seemed to us appropriate to commemorate Baade's seminal work in 1994, when it would have its 50-th anniversary, and to review its present status and also its role in contempory understanding. While we were in Leiden for an administrative committee, we discussed the matter again and over beers on October 29, 1991 we decided the take the initiative for an IAU Symposium on the subject during the 1994 IAU General Assembly in Den Haag, the Netherlands.

In the early summer of '89 a very informal meeting on the bulge of our Galaxy was held in Leiden. During that meeting Michael Rich proposed to hold a more properly organised symposium on "Galactic Bulges" in a few years time. After some discussion a Scientific Organising Committee was founded and after some manoeuvring a chairman was chosen, a local organiser was assigned and two editors were given instructions. A good thing about the location of the meeting was that Ghent is a very beautiful city and had never before hosted an IAU symposium. It could be that this, plus the fact that he is a very keen amateur astronomer led H. M. the King of Belgium to offer his patronage to the meeting - an offer that we gratefully and - we hope - gracefully accepted. The meeting took place at a resort some 15 km outside Ghent. Most participants were housed on the premises - a very convenient situation. This feeling of togeth erness made up for the small shortcomings of the lecture room, which is normally used as a sports hall. The weather was fair, except on the day of the barbecue when pouring rain forced us to go inside.

In July 1992, over 300 astronomers attended the Third Tetons Summer School on the subject of The Environment and Evolution of Galaxies'. This book presents 28 papers based on invited review talks and a panel discussion on The Nature of High Redshift Objects'. The major themes include: the Interstellar and Intergalactic Medium, Galaxy Formation and Evolution, Cooling Flows, Quasars and Radiation Backgrounds, and Interactions between Galaxies/AGNs and their Environment. Recent advances with the ROSAT, COBE and Hubble Space Telescope are discussed, together with current theoretical developments. The tutorial nature of the papers make this book a valuable supplement for professional astonomers, graduate students, and senior undergraduates. As with previous Tetons conferences, this book provides both the current state of observational and theoretical research and material complementary to courses in extragalactic and interstellar astrophysics.

A complete and comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The text presents an overview of the models developed to explain the stability, dynamics and evolution of the stars, and great care is taken to detail the various stages in a star's life. The authors have succeeded in producing a unique text based on their own pioneering work in stellar modeling.
Since its publication, this textbook has come to be considered a classic by both readers and teachers in astrophysics. This study edition is intended for students in astronomy and physics alike.

Planetary nebulae are a keystone for the understanding of the evolution of stars, for deep insights into the physical processes prevailing in highly excited dilute nebulae, and for the chemical evolution in galaxies. These objects, displaying an intriguing morphology, have a `short' lifetime of a few tens of thousands of years, and have become one of the best studied classes of celestial sources. However, despite large and successful efforts from both the observational and theoretical side, planetary nebulae still keep some of their secrets (like the widely unknown distances) and will undoubtedly also be objects of thorough investigations in the years to come.

MUL.APIN, written sometime before the 8th century BC, was the most widely copied astronomical text in ancient Mesopotamia: a compendium including information such as star lists, descriptions of planetary phases, mathematical schemes for the length of day and night, a discussion of the luni-solar calendar and rules for intercalation, and a short collection of celestial omens. This book contains an introductory essay, followed by a new edition of the text and a facing-page transliteration and English translation. Finally, the book contains a new and detailed commentary on the text. This is a fascinating study, and an important resource for anyone interested in the history of astronomy.

This book contains the proceedings of IAU Symposium No. 151 `Evolutionary Processes in Interacting Binary Stars,' which was held from 5 to 9 August 1991 in Cordoba, Argentina. The primary aim of this conference was to review and evaluate our current understanding of the evolutionary processes in wide variety of interacting binary stars from their births to their deaths. Subjects included the formation of binaries, mass flow and transfer, accretion processes, and binaries with collapsed components, such as novae, X-ray binaries and binary pulsars. As the field covered is both broad and diverse, there were in all thirty-seven invited talks; sixty-two contributed papers were also presented. In addition, these proceedings contain comments from a panel discussion of the major unsolved problems of interacting binary stars.

One approach to learning about stellar populations is to study them at three different levels of resolution. First in our own Galaxy; secondly from nearby galaxies where stars can still be resolved; and thirdly in remote galaxies in which the stellar population can only be studied in integrated light. This IAU Symposium covered the entire range of galaxies in its study of their stellar populations. Interspersed with theoretical papers, the wealth of observational results provides an important state-of-the-art presentation of the progress that has been made in this field.

This timely volume provides comprehensive coverage of all aspects of cosmology and extragalactic astronomy at an advanced level. Beginning with an overview of the key observational results and necessary terminology, it covers important topics: the theory of galactic structure and galactic dynamics, structure formation, cosmic microwave background radiation, formation of luminous galaxies in the universe, intergalactic medium and active galactic nuclei. This self-contained text has a modular structure, and contains over one hundred worked exercises. It can be used alone, or in conjunction with the previous two accompanying volumes (Volume I: Astrophysical Processes, and Volume II: Stars and Stellar Systems).

The origin of stars is one of the principle mysteries of nature. During the last two decades advances in technology have enabled more progress to be made in the quest to understand stellar origins than at any other time in history. The study of star formation has developed into one of the most important branches of mod ern astrophysical research. A large body of observational data and a considerable literat ure now exist concerning this topic and a 1arge community of international astronomers and physicists devote their efforts attempting to decipher the secrets of stellar birth. Yet, the young astronomerjphysicist or more advanced researcher desiring to obtain a basic background in this area of research must sift through a very diverse and sometimes bewildering literature. A literature which includes research in many discip1ines and sub discip1ines of classical astrophysics from stel lar structure to the interstellar medium and encompasses the entire range of the electromagnetic spectrum from radio to gamma rays. Often, the reward of a suc cessfu1 foray through the current literature is the realization that the results can be obsolete and outdated as soon as the ink is dry in the journal or the conference proceeding in which they are published.

Classical stellar evolution theories have undergone some drastic changes in recent decades. New insights into the development of stellar interiors were obtained from studying stars in various stages of their lives, as well as with the help of fast computers, which gave a boost to the branch of numerical modelling of stellular structure and evolution. This book is divided into two parts. The first part deals with the general aspects of stellular structure and evolution including a chapter on numerical modelling. The second part deals with specific evolutionary aspects of single and binary stars with a variety of masses. The last chapter gives several models of stars with specific masses. The book is intended as an introduction for students, as well as a reference for researchers.

More than two-thirds of stars belong to multiple stellar systems. Binary stars are considered now as one of the best constraints on stellar formation models. Not only do binaries keep memory of their birth conditions but their orbit will also be subjected to changes by tidal effects, wind accretion and encounters in clusters. Certainly the correlation between orbital eccentricity and period is a clue to our understanding of double star history. These proceedings aim to disentangle evidence of stellar formation from later physical evolution. Each article in this 1992 volume is a paper that was read at a meeting organized to honour Dr Roger Griffin of the University of Cambridge for his pioneer work in galactic astronomy, dynamics of clusters and study on binary stars due to his cross-correlation technique to determine stellar radial velocities.

Highly ionized atoms in the general interstellar gas of the galactic disk were first detected through interstellar absorption line observations of 0 VI with the Copernicus satellite (Rogerson et al. 1973). Survey measurements by Jenkins (1978) of interstellar 0 VI absorption toward 72 stars demonstrated the general presence of 0 VI in the interstellar medium of the galactic disk. This researcIi. and parallel observational studies of the soft X-ra}' background (Williamson et al. 1974; McCammon et al. 1983; Marshall and ClarK 1984) provided direct evidence for the existence of hot low density gas in the mterstellar medium of the galactic disk. The extension of the aDsorption line studies to the distant gas of the galactic halo required the launch of the International Ultraviolet Explorer (IUE) satellite in 1978. The first measures of highly ionized gas m the galactic halo were obtained with the IDE when it was used to record high resolution spectra of bright stars in the Large Magellanic Cloud (Savage and de Boer 1979). Those early spectra revealed the presence of absorption by Si IV and C IV in the galactic nalo and have been followed by a number of surveys with IUE of nighly ionized gas in the galactic disk and halo (Savage and de Boer 1981; Pettini and West 1982; Savage and Massa 1987). The study of UV emission from highly ionized gas in the halo has progressed more slowly because of the intrinsic faintness of the emission.

One of the most spectacular discoveries of molecular astronomy has been the detection of maser emission. The same radiation that is generated in the laboratory only with elaborate, special equipment occurs naturally in interstellar space. This intense radiation probes the smallest structures that can be studied with radio telescopes. By a fortunate coincidence maser radiation is generated in both star forming regions and the envelopes of late-type stars. The early and late stages in the life of a star are considered to be the most interesting phases of stellar evolution. Maser emission has also been detected in external galaxies. This book provides an extensive coverage of the interstellar maser phenomenon. A precondition for maser action is departure from thermal equilibrium. The book therefore starts with a detailed coverage of the basic background concepts required for an understanding of line formation and radiative transfer. It goes on to describe the theoretical and phenomenological aspects of interstellar masers, their formation sites and the inversion mechanisms. The book will interest active researchers in astronomy and astrophysics as well as in other areas of physics. It is suitable as a textbook in a graduate course and will enable a graduate student to embark on research projects in this exciting area in particular, and molecular radio astronomy in general.

Symposium 148 "The Magellanic Clouds and their Dynamical Interaction with the Milky Way" was the first IAU Symposium held in Australia since 1973. In all, 23 countries were represented by 149 participants. The Symposium was held from July 9 to 13, 1990 at Womens College, the University of Sydney. The last symposium on the Magellanic Clouds' was held in 1983 in Ttibingen, Germany. Since then new ground-and satellite-based instruments have become available. A range of results from these instruments were presented at IAU Symposium 148 and are published in these proceedings. IAU Symposium 148 was timed to coincide with the commissioning of the Australia Telescope, and indeed, a few of the first results from that instrument were presented at this Symposium Over the next decade the Australia Telescope is destined to make a major impact on Magellanic Cloud research. Papers are arranged in five main sections reflecting the Symposium timetable: * Large-Scale Structure and Kinematics * Star Formation and Clustering * Stellar Evolution * The Interstellar Medium * The LMC-SMC-Galaxy System These are preceeded by both the introduction to and the summary of the Symposium. Questions and answers from the oral sessions are reproduced at the end of each section.

G. MICHAUD Dipartement de Physique Universiti de Montrial c. P. 6128, succursale A Montrial, Que. , H3C 317 Canada The aim of IAU Symposium 145 was to use the photospheric abundances of the chemical elements to give us some hint of the past evolution and of the current structure of stars. At the invitation on the Bulgarian Academy o/Sciences, it brought together one hundred and fifty one scientists from 21 countries to 71atni Pjasaci (Golden Sands), Bulgaria, for a five day meeting. The processes discussed included accretion, mass loss, mass exchange, convection, turbulence, meridional circulation, and diffusion in addition to nuclear reactions. Observationally, spectroscopy was involved. New telescopes and instruments have considerably extended the scope of spectroscopy over the last few years. Space telescopes, such as IUE, have allowed the development of far UV spectroscopy. The access to the infrared has proven critical for probing cool stars. Large ground based telescopes have allowed fainter objects to be observed especially when they are equipped with more efficient detectors such as CCDs and Reticons. The co-adding of digitalized photographic plates has extended their usefulness. It has become possible to make high resolution, high signal to noise observations of objects that could only be observed at low resolution in former days. Weak lines can now be measured with accuracy, allowing the precise determination of the abundances of elements as rare as lithium and the determination of precise limits to isotopic ratios.

A few years ago, a motivation for organizing one more IAU Symposium on star for mation in Grenoble, was the anticipated completion of the IRAM interferometer on the Plateau de Bures, close to Grenoble. This choice was also a sort of late celebration of the genius of Joseph Fourier, born in Grenoble, whose work is the very fondation of in terferometry. At the time when we finally announced the advent of this conference, the first reactions we got from the community were expressions of saturation and even reject, the Symposium being unfortunately scheduled almost simultaneously as two other major meetings on closely related topics, and sponsored by different organizations. A wave of disappointment then reached the organizers. Some of us were enthusiastic enough to help the others overcome their discouragement. Let them be thanked here. There was, indeed, a deeper motivation for organizing this conference. It was to trigger the meeting and communication of physicists and astrophysicists since many of the difficulties met now in understanding the physics of the interstellar medium and its evolution toward star formation are common to several, if not most, other fields of physics. They are assigned to one origin: complexity.

Proceedings of the 146th Symposium of the International Astronomical Union, held in Paris, France, June 4-9, 1990

The first ideas for the symposium were generated in Brussels in the summer of 1986, dur ing exquisite lunches in between HST proposal consortium meetings. At the time it was expected that soon after the previous IAU symposium (No. 116) devoted to luminous hot massive stars, a bonanza of new exciting observational material would become available, together with significant advances on the theoretical front. Also it was felt that Wolf Rayet stars should feature predominantly, because that had not been the case since IAU Symposium No. 99 in 1981. Tradition requires that IAU symposia on hot massive stars take place in high lumi nosity beach resorts, and after Buenos Aires, Qualicum Beach, Cozumel and Porto Heli, Bali sounded like a reasonable place. Therefore we were only too pleased with the invitation of the Indonesian astronomical community to host the symposium in Sanur (Denpasar). The aim of the symposium was to bring together both observers and theoreticians active in the field of Wolf-Rayet stars and related objects, to present and discuss their recent results, in order to expose to what extent consensus exists as to the physical and chemical properties of Wolf-Rayet stars, their evolutionary status and their interrelations with other massive stars in galaxies."