The general discussions of the roles of photometric and spectroscopic classification at Cordoba in 1971 (lAU Symposium No. 50), and of the calibration of classification indices at Geneva in 1972 (IAU Symposium No. 54), revealed clearly the steadily in creasing importance of abundance parameters. The multipliCity of these, however, raised so many new problems that it was logical that the 1975 meeting at Lausanne should be concerned with ways in which differences in abundance affect both spectral types and photometric indices. Commissions 29 and 36 joined with Commission 45 in sponsoring this Symposium. Since the date of the meeting came shortly after the formal retirement of Professor William W. Morgan from the University of Chicago, it was quickly agreed that this meeting should be dedicated to him in recognition of his unique contributions to spectral classification. In the opening paper of the Symposium Dr. Bengt Stromgren has summarized these. To his remarks we should add only that it was about 1940 that Morgan first distinguished the group of G- and K-type stars with weak CN bands and metallic lines - stars which have since been recognized as having the abundance of all metals relative to hydrogen much lower than in stars of the solar population. Spectra of two of these, HD 81192 (Boss 2527) and 8 Lep, were later shown as examples of the group in the Yerkes Atlas of 1943."

The idea of holding this Symposium has its origin in a conversation with G. Con to poulos during the winter of 1973. It was then clear that the progress realized in Stellar Dynamics since the Thessaloniki symposium had given a new shape to the field. Other meetings such as the C. N. R. S. colloquium held in Paris in 1967 or the LA. V. colloquium held in Cambridge, England, in 1970 had in the meantime given opportunities to review the advances achieved in several branches of this field. We thought that time had come to organize a general confrontation of the new results obtained in the approach of the gravitational N-body problem by different methods, in the investigation of spherical and flattened systems, in the comparisons with ob servations and in more theoretical speculations on orbits, integrals of motion, dense nuclei or relativistic stellar dynamics. Things were made easy by the support of Commissions 33 and 37 which welcomed the proposition and by 1. R. King who accepted to act as Chairman of the Scientific Organizing Committee. The final decision to meet in Besan'Yon was taken during the XVth General Assembly of the LA. U. in Sydney in August 1973. The members of the Organizing Committee were: 1. R. King (Chairman), G. Con topoulos, A. Hayli, M. Henon, G. Hori, D. Lynden-Bell, L. Perek, L. Spitzer, R. Wielen, Ya. Zel'dovich while the members of the Local Committee were: A."

This book contains a set of articles based on a session of the annual meeting of the American Association for the Advancement of Science held in San Francisco in February, 1974. The reason for the meeting arose from the need to communicate to the largest possible scientific community the dramatic advances which have been made in recent years in the understanding of collapsed objects: neutron stars and black holes. Thanks to an unprecedented resonance between X-ray, y-ray, radio and optical astronomy and important new theoretical developments in relativistic astro physics, a new deep understanding has been acquired of the physical processes oc curring in the late stages of evolution of stars. This knowledge may be one of the greatest conquests of man's understanding of nature in this century. This book aims to give an essential and up-to-date view in this field. The analysis of the physics and astrophysics of neutron stars and black holes is here attacked from both theoretical and experimental points of view. In the experimental field we range from the reviews and catalogues of galactic X-ray sources (R. Gursky and E. Schreier) and pulsars (E. Groth) to the observations of the optical counter part of X-ray sources (P. Boynton) to finally the recently discovered gamma-ray bursts (I. Strong) and pulse astronomy R. B. Partridge)."

Colloquia and symposia have almost become a tradition among the variable-star astronomers; those held more or less regularly at Bamberg and Budapest have become well known. For a change, this time the organizing committee of Commission 27 decided to hold an LA. U. symposium in Moscow and to adopt as a special topic the relation between variable stars and the evolution of stars and stellar systems. This symposium, No. 67 in the LA. U. series, was prepared by two committees, a by B. V. Kukarkin, and a local one with V. A. Ambartsumian scientific one chaired as chairman, and G. S. Khromov as executive secretary. It was held in Moscow at the Physical and Astronomical Institutes of the Lomonosov University from July 29 to August 4, 1974. The symposium was opened with three short welcoming speeches by V. A. Ambartsu mian, J. M. Ternov (vice-rector of Moscow University), and B. V. Kukarkin. All three stressed the importance of the study of variable stars in connection with the evolution of stars and stellar systems, the role of the Russian astronomers in these studies, and the necessity of international cooperation."

'Galactic Radio Astronomy' was chosen as the subject of this Symposium, which was held in conjunction with the IAU General Assembly that took place in Sydney in August 1973, largely because it is a very suitable Southern Hemisphere topic. This results in part from the advantages of a southern location in studying the Galaxy and in part from the long association of Australia with radio astronomy. Following the General Assembly, the Symposium was held at the Surf air Inter national Hotel in Maroochydore, Queensland, from 3 to 7 September, 1973. The conference participants were effectively isolated from the rest of the world during the Symposium, and the excellent spring weather and geographical situation led to the development of an unusually good rapport. The Symposium was sponsored by Commissions 40, 33, and 34. The Organizing Committee was composed of A. H. Barrett (chairman), J. E. Baldwin, D. S. Heeschen, F. J. Kerr, J. Lequeux, S. W. McCuskey, P. G. Mezger, B. Y. Mills, Yu. N. Parijskij, B. J. Robinson, H. van der Laan, and H. F. Weaver. The Local Committee, consisting ofB. J. Robinson, N. G. Seddon, and P. J. Kelly, looked after the arrangements in very fine style. The Symposium was supported financially by the IAU, the Australian Academy o Science, the CSIRO Division of Radiophysics, Union Carbide Australia Limited, and the Science Foundation for Physics within the University of Sydney."

The XXth meeting of the IAU in Australia in 1973 made the venue for the IAU Symposium No. 59 on Stellar Instability and Evolution, at Mount Stromlo Obser vatory on August 16-18, a very appropriate one. Many of the current and former staff of Mount Stromlo Observatory (operated by the Australian National Univer sity) have specialized in the study of variable stars and it was with considerable pleasure that Mount Stromlo Observatory accepted the responsibility of hosting and making the local arrangements for IAU Symposium No. 59. The Scientific Organizing Committee was particularly active in formulating the program and comprised Drs N. Baker, P. Demarque, M. Feast, G. Herbig, I. Iben, P. Ledoux, J. Ostriker and E. Schatzman. The aim of the Committee was to integrate the review and contributed papers on the particular instability mechanisms involved, their observational manifestations and their relation to the internal structure of the star as inferred from its evolutionary history. The Local Organizing Committee consisted of Miss P. Petrie and A. W. Rodgers."

Proceedings of IAU Symposium No. 58 held in Canberra, Australia, August 12-15, 1973

The idea of the symposium came during the XVllth General Assembly of the IAU at Montreal. The Working Group on Be stars adopted both the proposal of holding a meeting, and of having it at the Universitats- sternwarte Munich. The meeting was organized under the auspices of IAU Comm. 29 (Stel- lar Spectra) and the sponsorship of Comm. 45 (Stellar Classification). The Scientific Organizing Committee was composed of Mercedes Jaschek (chairman), W. Bonsack, C. de Loore, A. Feinstein, H. G. Groth, P. Harmanec, L. Houziaux, A. M. Hubert-De1p1ace, L. S. Luud, A. Slettebak and A. Underhill. The members of this committee are to be thanked for their devotion to the organization of what turned out to be a very successful meeting. The program was organized on an observational approach, comprising sessions on photometry, polarization, spectroscopy, infrared observations, rotation and binarity, X-ray observations, UV observations and mass loss, and atmospheric models. Each session started with an invited summary paper, followed by a number of contributions. The different sessions were chaired by A. Feinstein, R. Sta1io, C. de Loore, Ch. Fehrenbach, J. P. Swings, C. Jaschek, A. Sapar, G. T. Traving, M. de Groot and H. G. Groth. Upon request of the Working Group., a special session was devoted to bibliographic problems and observing campaigns. The Dean of the Faculty for Physics 0.GBP the Ludwig-Maximilians-, Universitat welcomed the participants at the beginning of the Symposium. The meeting was closed by a summary talk, delivered by ~. P. Snow.

In connection with arranging IAU Symposium No. 50 on 'Spectral Classification and Multicolour Photometry', sponsored by Commissions 45 and 25, it was decided to exclude all calibration problems. Instead it was agreed that we should attempt to arrange a separate symposium, dealing with the fundamental problems of the cali bration of absolute magnitudes and temperatures of stars. The Executive Committee of the IAU accepted our proposal, and IAU Symposium No. 54 was held in Geneva on September 12-15, 1972, sponsored by thefollowing IAU Commissions: 24, 25, 29, 33, 35, 37,44 and 45. It was attended by about 90 scientists representing 16 countries. The Symposium was divided into eight sessions. Each session started with a review paper by an invited speaker; this was followed by a general discussion including a few contributed papers. The contents of the present volume follow closely the programmes of the individual sessions of the Symposium. Most of the recorded discussions have been kept, and only in a few cases have the order of questions and comments been altered so as to obtain more homogeneity in the presentation."

The proposal to organize a Symposium on circumstellar matter and extended atmo spheres in binary systems was first made by the Dominion Astrophysical Observatory to the Executive Committee of the International Astronomical Union in the summer of 1969. It received the support of the presidents of Commissions 29 (Stellar Spectra), 30 (Radial Velocities), 36 (Stellar Atmospheres), and 42 (Photometric Double Stars). Approval in principle was given by the Executive Committee almost immediately, and the Committee further suggested that the Symposium be officially designated the Struve Memorial Symposium. Final approval was given at the time of the 1970 General Assembly of the Union. when the dates of the Symposium were set for August or September, 1972. The Organizing Committee set up consisted of K. O. Wright (Chairman), A. H. Batten, K. -H. B6hm, A. A. Boyarchuk, G. Larsson-Leander, and M. Plavec. In addition, J. Sahade and F. B. Wood acted as advisory members. Local organization was entrusted to a committee consisting of A. H. Batten, E. K. Lee, and C. D. Scarfe. The final dates selected were September 6-12, 1972, and the Sym posium was held at the Island Hall Hotel, Parksville, B. C., on Vancouver Island some 90 miles from Victoria. The Organizing Committee attempted to arrange a Symposium of the type in which no contributed papers would be presented and discussion would range as widely as possible over the field covered by the six invited review papers."

We have in this volume, compiled a connected account of the proceedings of the Symposium on Wolf-Rayet and High-Temperature Stars held at Buenos Aires. The Organizing Committee had assigned broad areas of topical interest to be reviewed by invited speakers. Each of these presentations was followed by lengthy discussions that were tape recorded and transcribed later. These discussions have been edited only to a limited extent. We have shortened them and rearranged them to bring about a greater coherence. We have, however, attempted to retain the tenor of the discussions, the flavour of impromptu remarks and the continuity of an argument. Much of the success of such a venture depends on the contributors to the discussions. To be able to make these thoughts available to a larger audience has been the task of those re sponsible for the elaborate tape recording of the proceedings. We thank those at the Instituto de Astronomia y Fisica del Espacio for the efficient way in which this re sponsibility has been discharged. Many at Buenos Aires and Kodaikanal have contrib uted efficient assistance to the preparation of this volume and we are deeply indebted for their help. In particular, two amongst these, Nora Martinez and A. M. Batcha have contributed overwhelmingly both to the organization of the symposium and the final preparation of the symposium volume. Financial support for this symposium came from the International Astronomical Union and the Argentine National Research Council."

Proceedings of IAU Symposium No. 53 held in Boulder, Colorado, 21-26 August 1972

Radio pulsars are rapidly rotating highly magnetized neutron stars. Studies of these fascinating objects have provided applications in solid-state physics, general relativity, galactic astronomy, astrometry, planetary physics and even cosmology. Most of these applications and much of what we know about neutron stars are derived from single-dish radio observations using state-of-the-art receivers and data acquisition systems. This comprehensive 2004 book is a unique resource that brings together the key observational techniques, background information and a review of results, including the discovery of a double pulsar system. Useful software tools are provided which can be used to analyse example data, made available on a related website. This work will be of great value not only to graduate students but also to researchers wishing to carry out and interpret a wide variety of radio pulsar observations.

Dive into a mind-bending exploration of the physics of black holes Black holes, predicted by Albert Einstein's general theory of relativity more than a century ago, have long intrigued scientists and the public with their bizarre and fantastical properties. Although Einstein understood that black holes were mathematical solutions to his equations, he never accepted their physical reality--a viewpoint many shared. This all changed in the 1960s and 1970s, when a deeper conceptual understanding of black holes developed just as new observations revealed the existence of quasars and X-ray binary star systems, whose mysterious properties could be explained by the presence of black holes. Black holes have since been the subject of intense research--and the physics governing how they behave and affect their surroundings is stranger and more mind-bending than any fiction. After introducing the basics of the special and general theories of relativity, this book describes black holes both as astrophysical objects and theoretical "laboratories" in which physicists can test their understanding of gravitational, quantum, and thermal physics. From Schwarzschild black holes to rotating and colliding black holes, and from gravitational radiation to Hawking radiation and information loss, Steven Gubser and Frans Pretorius use creative thought experiments and analogies to explain their subject accessibly. They also describe the decades-long quest to observe the universe in gravitational waves, which recently resulted in the LIGO observatories' detection of the distinctive gravitational wave "chirp" of two colliding black holes--the first direct observation of black holes' existence. The Little Book of Black Holes takes readers deep into the mysterious heart of the subject, offering rare clarity of insight into the physics that makes black holes simple yet destructive manifestations of geometric destiny.

Based on the very popular liberal arts course Bob Bless has taught at University of Wisconsin for many years, this book provides a rich, historical approach to introductory astronomy. It is ideal for use in an introductory astronomy course for nonmajors. In the fifteen years since the first edition of this text was published, several new concepts such as dark matter, dark energy, and an incredible expansion of the universe (inflation) have been developed. Furthermore, many of the exotic effects predicted by General Relativity (e.g. black holes, warped space) have gone from being interesting theoretical speculations to useful practical tools for understanding the universe. This book aims to give an overview of astronomy, but in such a way that the non-science major can get a feeling for how science actually developed with its false starts and wrong turns, which observational evidence eventually corrected, and also to describe the incredible recent developments in our understanding of the physical universe. Several chapters of this 2nd edition have been extensively revised to include these recent developments. Because it has become increasingly difficult to "cover" all of astronomy in a one-semester course, this edition has largely omitted coverage of the physical nature of the objects in our, and other, planetary systems, although a discussion of the possibility of life elsewhere closes the book.

Illustrated with breathtaking images of the Solar System and of the Universe around it, this book explores how the discoveries within the Solar System and of exoplanets far beyond it come together to help us understand the habitability of Earth, and how these findings guide the search for exoplanets that could support life. The author highlights how, within two decades of the discovery of the first planets outside the Solar System in the 1990s, scientists concluded that planets are so common that most stars are orbited by them. The lives of exoplanets and their stars, as of our Solar System and its Sun, are inextricably interwoven. Stars are the seeds around which planets form, and they provide light and warmth for as long as they shine. At the end of their lives, stars expel massive amounts of newly forged elements into deep space, and that ejected material is incorporated into subsequent generations of planets. How do we learn about these distant worlds? What does the exploration of other planets tell us about Earth? Can we find out what the distant future may have in store for us? What do we know about exoworlds and starbirth, and where do migrating hot Jupiters, polluted white dwarfs, and free-roaming nomad planets fit in? And what does all that have to do with the habitability of Earth, the possibility of finding extraterrestrial life, and the operation of the globe-spanning network of the sciences?

'fascinating' Brian Cox This is the story of citizen science. Where once astronomers sat at the controls of giant telescopes in remote locations, praying for clear skies, now they have no need to budge from their desks, as data arrives in their inbox. And what they receive is overwhelming; projects now being built provide more data in a few nights than in the whole of humanity's history of observing the Universe. It's not just astronomy either-dealing with this deluge of data is the major challenge for scientists at CERN, and for biologists who use automated cameras to spy on animals in their natural habitats. Artificial intelligence is one part of the solution-but will it spell the end of human involvement in scientific discovery? No, argues Chris Lintott. We humans still have unique capabilities to bring to bear-our curiosity, our capacity for wonder, and, most importantly, our capacity for surprise. It seems that humans and computers working together do better than computers can on their own. But with so much scientific data, you need a lot of scientists-a crowd, in fact. Lintott found such a crowd in the Zooniverse, the web-based project that allows hundreds of thousands of enthusiastic volunteers to contribute to science. In this book, Lintott describes the exciting discoveries that people all over the world have made, from galaxies to pulsars, exoplanets to moons, and from penguin behaviour to old ship's logs. This approach builds on a long history of so-called 'citizen science', given new power by fast internet and distributed data. Discovery is no longer the remit only of scientists in specialist labs or academics in ivory towers. It's something we can all take part in. As Lintott shows, it's a wonderful way to engage with science, yielding new insights daily. You, too, can help explore the Universe in your lunch hour.

From time immemorial, poets and philosophers have looked in awe and wonder at the Universe. Such awe is shared by astrophysicists, too, as they seek to understand its nature, and whether it has any limits. In The Infinite Cosmos, Joseph Silk, Savilian Professor of Astronomy at Oxford University, cosmologist and well-known science writer, brings together the modern understanding of the Universe, its structure, its evolution, and its possible fate, combining the latest from theory and observation. The narrative is peppered with quotations from literature and philosophy, and reflects, too, on the process of scientific discovery, and the implications of our discoveries.

This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium; and star formation. While it is assumed that the reader has a background in undergraduate-level physics, including some prior exposure to atomic and molecular physics, statistical mechanics, and electromagnetism, the first six chapters of the book include a review of the basic physics that is used in later chapters. This graduate-level textbook includes references for further reading, and serves as an invaluable resource for working astrophysicists. * Essential textbook on the physics of the interstellar and intergalactic medium * Based on a course taught by the author for more than twenty years at Princeton University * Covers radiative processes, fluid dynamics, cosmic rays, astrochemistry, interstellar dust, and more * Discusses the physical state and distribution of the ionized, atomic, and molecular phases of the interstellar medium * Reviews diagnostics using emission and absorption lines * Features color illustrations and detailed reference materials in appendices * Instructor's manual with problems and solutions (available only to teachers)

The Cambridge Double Star Atlas is back! It is the first and only atlas of physical double stars that can be viewed with amateur astronomical instruments. Completely rewritten, this new edition explains the latest research into double stars, and looks at the equipment, techniques and opportunities that will enable you to discover, observe and measure them. The target list has been completely revised and extended to 2500 binary or multiple systems. Each system is described with the most recent and accurate data from the authoritative Washington Double Star Catalog, including the HD and SAO numbers that are most useful in our digital age. Hundreds of remarks explain the attributes of local, rapidly changing, often measured or known orbital systems. The color atlas charts by Wil Tirion have been updated to help you easily find and identify the target systems, as well as other deep-sky objects. This is an essential reference for double star observers.

Present-day elliptical, spiral and irregular galaxies are large systems made of stars, gas and dark matter. Their properties result from a variety of physical processes that have occurred during the nearly fourteen billion years since the Big Bang. This comprehensive textbook, which bridges the gap between introductory and specialized texts, explains the key physical processes of galaxy formation, from the cosmological recombination of primordial gas to the evolution of the different galaxies that we observe in the Universe today. In a logical sequence, the book introduces cosmology, illustrates the properties of galaxies in the present-day Universe, then explains the physical processes behind galaxy formation in the cosmological context, taking into account the most recent developments in this field. The text ends on how to find distant galaxies with multi-wavelength observations, and how to extract the physical and evolutionary properties based on imaging and spectroscopic data.

"An Introduction to Stellar Astrophysics" aspires to provide the reader with an intermediate knowledge on stars whilst focusing mostly on the explanation of the functioning of stars by using basic physical concepts and observational results.

The book is divided into seven chapters, featuring both core and optional content: Basic conceptsStellar FormationRadiative Transfer in StarsStellar AtmospheresStellar InteriorsNucleosynthesis and Stellar Evolution andChemically Peculiar Stars and Diffusion.

Student-friendly features include: Detailed examples to help the reader better grasp the most important conceptsA list of exercises is given at the end of each chapter and answers to a selection of these are presented.Brief recalls of the most important physical concepts needed to properly understand stars.A summary for each chapterOptional and advanced sections are included which may be skipped without interfering with the flow of the core content.

This book is designed to cover the most important aspects of stellar astrophysics inside a one semester (or half-year) course and as such is relevant for advanced undergraduate students following a first course on stellar astrophysics, in physics or astronomy programs. It will also serve as a basic reference for a full-year course as well as for researchers working in related fields.

The first three billion years of cosmic time were the prime epoch of galaxy formation. Characterising galaxies at this epoch is therefore crucial to achieving a major goal of modern astrophysics: to understand how galaxies such as our Milky Way emerged from the primordial density fluctuations in the early Universe and how they evolved through cosmic time. Recent major international investments in observing facilities such as the Atacama Large Millimetre Array (ALMA) and the James Webb Space Telescope (JWST) promise to provide the next leap in our understanding of this topic. This volume gathers the scientific contributions to the International Astronomical Union Symposium 352, which was devoted to this topic. The community of theoretical and observational experts discuss how we can make the most of ALMA and JWST synergies in advancing our understanding of galaxy evolution in the young Universe.

Most elements are synthesized, or "cooked", by thermonuclear reactions in stars. The newly formed elements are released into the interstellar medium during a star's lifetime, and are subsequently incorporated into a new generation of stars, into the planets that form around the stars, and into the life forms that originate on the planets. Moreover, the energy we depend on for life originates from nuclear reactions that occur at the center of the Sun. Synthesis of the elements and nuclear energy production in stars are the topics of nuclear astrophysics, which is the subject of this book. It presents nuclear structure and reactions, thermonuclear reaction rates, experimental nuclear methods, and nucleosynthesis in detail. These topics are discussed in a coherent way, enabling the reader to grasp their interconnections intuitively. The book serves both as a textbook for advanced undergraduate and graduate students, with worked examples and end-of-chapter excercises, but also as a reference book for use by researchers working in the field of nuclear astrophysics.

Neutron stars, the most extreme state of matter yet confirmed, are responsible for much of the high-energy radiation detected in the universe. Meszaros provides a general overview of the physics of magnetized neutron stars, discusses in detail the radiation processes and transport properties relevant to the production and propagation of high-energy radiation in the outer layers of these objects, and reviews the observational properties and theoretical models of various types of neutron star sources.