There is hardly any field of human endeavour which is more fundamental than the study of our surroundings. We have always wanted to learn what was behind our horizon, beyond the next mountain, on the other side of the ocean, on the next planet, at the end of the Universe. We have come a long way since our early ancestors gazed upon the sky in amazement. Giant optical and radio telescopes now allow us to "see" the early epochs of the Universe, revealing phenomena beyond our comprehension. Spacecrafts with on-board astronomical instrumentation circle the Earth and fly to the limits of the Solar System, providing invaluable new information about nearby and distant objects. Many people have the intuitive feeling that it is "easier and better" to study the Universe from above the Earth's atmosphere. However, this is only partially true in as much as electromagnetic radiation of certain wavelengths (e.g. X-rays) does not penetrate the atmosphere and can only be studied from balloons and space crafts * The advent of space-borne astronomy has not made ground-based observations obsolete - on the contrary, it is only thanks to the combination of the two that we have now a vastly more comprehensive picture of the Universe than just a few decades ago.

The aim of the present book will be to provide a comprehensive account of our present knowledge of the theory of dynamical phenomena exhibited by elose binary systems; and on the basis of such phenomena as have been attested by available observations to outline probable evolutionary trends of such systems in the course of time. The evolution of the stars - motivated by nuelear as weIl as gravitation al energy sources - constitutes nowadays a well-established branch of stellar astronomy. No theo ries of such an evolution are as yet sufficently specific - let alone infallible - not to require continual tests by a confrontation of their consequences with the observed prop erties of actual stars at different stages of their evolution. The discriminating power of such tests depends, of course, on the range of information offered by the test objects. Single stars which move alone in space are now known to represent only a minority of objects constituting our Galaxy (cf. Chapter 1-2); and are, moreover, not very revealing of their basic physical characteristics - such as their masses or absolute dimensions. If there were no binary systems in the sky, the only star whose vital statistics would be fully known to us would be our Sun.

X-ray astronomers discovered the diffuse gas in clusters of galaxies about 20 years ago. It was later realized that the central gas density in some clusters, and in elliptical galaxies, is so high that radiative cooling is a significant energy loss. The cooling time of the gas decreases rapidly towards the centre of the cluster or galaxy and is less than a Hubble time within the innermost few hundred kiloparsecs. This results in a cooling flow in which the gas density rises in order to maintain pressure to support the weight of the overlying gas. The rate at which mass is deposited by the flow is inferred to be several hundreds of solar masses per year in some clusters. The fraction of clusters in which cooling flows are found may exceed 50 per cent. Small flows probably occur in most normal elliptical galaxies that are not in rich clusters. The implications of this simple phenomenon are profound, for we appear to be witnessing the ongoing formation of the central galaxy. In particular, since most of the gas is undetected once it cools below about 3 million K, it appears to form dark matter. There is no reason why it should be detectable with current techniques if each cooling proton only recombines once and the matter condenses into objects of low mass.

Proceedings of the 99th Colloquium of the International Astronomical Union, held in Balaton, Hungary, June 22-27, 1987

The idea to hold a conference on the Evolution of Close-Binary X-ray sources grew in the summer of 1984. At that time we were hoping that some new results would be harvested in the months to come which would stimulate further work. We were particularly looking towards the Euro pean X-ray Observatory, EXOSAT, for new contributions. How lucky we were; quite unexpected developments took place. Just prior to the conference, quasi-periodic oscillations (now known as QPO) were discovered in three bright low-mass X-ray binaries: GX 5-1, Sco X-1, and Cyg X-2. They played an important role at the meeting. The possibility that QPOs imply a neutron star magnetic dipole field, and a neutron star rotation period in the millisecond range, received a lot of attention. This is not surprising, as it lends support to the idea, suggested earlier, that the 6-msec binary radio pulsar PSR 1953+29 evolved from a stage in which it was a bright low-mass X-ray binary. There was special interest in the possibility of white dwarf collapse into a neutron star. This is a. particularly attractive way to form the bright low-mass X-ray binaries, often referred to as galactic bulge sources. It would allow for the possibility of a very young neutron star in a very old binary system. The relatively high magnetic fields that one could infer from QPO could then be explained."

A Platonic philosopher, Paracelsian chemist, Ovidian poet, and devoted family man, Tycho Brahe was the last Renaissance man and the first great organizer of modern science. This book provides the fullest portrait available of the research and cultural interests of the man who became the premier patron-practitioner of science in sixteenth-century Europe. Starting from Brahe's well reputed role of astronomer, author Christianson adds lesser known details of the man who was both a geodetic surveyor as well as a garden designer, and ultimately established a new role of scientist as administrator, active reformer, and natural philosopher. Coverage reveals how from his private island in Denmark, Brahe used patronage, printing, friendship, and marriage to incorporate men and women skilled in science, technology, and the fine arts into his program of cosmic reform. Through their teamwork, they achieved breakthroughs in astronomy, scientific method, and research organization that were essential to the birth of modern science. Also included are over 100 capsule biographies of Tycho's clients, coworkers, and friends, including Johannes Kepler, Willebrord Snel, Willem Blaeu, several bishops, and numerous technical specialists all of whom helped shape the culture of the Scientific Revolution. This pioneering exposition will appeal to science history buffs, especially those with an interest in the late Renaissance and will inspire anyone who has a passion for science and a penchant for the world of ideas. John Robert Christianson received his Ph.D. from the University of Minnesota. He was dubbed Knight of the Royal Norwegian Order of Merit by King Harald II in 1995.

Clusters and superclusters of galaxies are the largest objects in the Universe. They have been the subject of intense observational studies at a variety of wavelengths, from radio to X-ray which has provoked much theoretical debate and advanced our understanding of the recent evolution of the large-scale structure of the Universe. The current status of the subject is reviewed in this volume by active researchers who lectured at a NATO Advanced Study Institute held in Cambridge, England in July 1991. Much of the material is presented in a pedagogical manner and will appeal to scientists, astronomers and graduate students interested in extragalactic astronomy.

Historically, the discovery of tools, or evidence that tools have been used, has been taken as proof of human activity; certainly the invention and spread of new tools has been a critical marker of human progress and has increased our ability to observe, measure, and understand the physical world. In astronomy the tools are telescopes and the optical and electronic instruments that support them. The use of the telescope by Galileo marked the beginning of a new and productive way to study and understand the universe in which we live. The effects of this new tool on what we can see, and how we see ourselves, are well known. However, after almost four centuries of developing ever more sensitive and subtle instruments as tools for astronomy, it might have been expected that only a few minor improvements would remain to be made, or that possibly the law of diminishing returns would have taken effect. On the contrary, the new instruments and ideas for new instruments described in this book make it clear that the rate of progress has not diminished, and that this subject is still as exciting and productive as ever. Instrumentation for Ground-Based Optical Astronomy was chosen as the theme for the Ninth Santa Cruz Summer Workshop in Astronomy and Astrophysics.

ASTRONOMICAL ECLIPSE PHENOMENA In looking over the long history of human science from time immemorial to our own times, it is impossible to overestimate the role played in it by the phenomena of eclipses of the celestial bodies-both within our solar system as well as in the stellar universe at large. Not later than in the 4th century B. C. , the observed features of the shadow cast on the Moon by the Earth during eclipses led Aristotle (384-322 B. C. ) to formulate the first scientific proof worthy of that name of the spherical shape of the Earth; and only somewhat later, the eclipses of the Sun provided Aristarchos (in the early part of the 3rd century B. C. ) or Hipparchos (2nd half ofthe same century) with the geometric means to ascertain the distance which separates the Earth from the Sun. In the 17th century A. D. (in 1676, to be exact) the timings of the eclipses of the satellites of Jupiter by their central planet enabled Olaf Romer to discover that the velocity with which light propagates through space is finite.

Within the framework of Ispra Courses, a course on "Applications of Remote Sensing to Agrometeorology" was held from April 6th to 10th, 1987 at the Joint Research Centre of the European Communities, Ispra Italy. The purpose of the course was to familiarize scientists, active in Agrometeorology and related fields, with remote sensing techniques and their potential applications in their respective disciplines. Conventional ground investigations in various fields of natural sciences such as hydrology, pedology and agrometeorology can be supple mented by a range of instruments carried by airborne or earth orbiting platforms. The last few years, in particular, have seen many developments in this respect and a growing amount of information can now be derived not only from dedicated earth resources satellites such as the LANDSAT and SPOT, but also from other platforms such as METEOSAT and the series of NOAA-TIROS. Future platforms (ERS-l, Space Station, etc.) with their advanced sensors will further broaden the range of applications open to the investigators. The use of these data sources, together with field investigations, can lead, at a reduced cost, to a better characterization of the spatial and temporal properties of natural systems."

Recent years have witnessed the expansion and multiplication of the observations of star formation and fragmentation accompanied by a consequent growth in the study of the underlying physical processes, the chemistry, the sites, the times, etc. Moreover, recent studies have shown that the formation of stars is likely to share many features with the formation of other self-gravitating objects. The present volume, therefore, discusses the formation of such objects in a systematic and comparative manner.

Peter P. Eggleton and James E. Pringle Institute of Astronomy Madingley Road Cambridge England The 1970's can be described, in retrospect, as the "Decade of the Close Binary." Exciting observations with new technology, combined with classical work, both observational and theoretical, convinced the astronomical world that binary interaction of various kinds is not only interesting but common. Indeed, by 1975 almost anything unusual had a good chance of being interpreted as due to binary interaction. But astronomers are seldom overwhelmed by speculation, even their own, and solid observational work has confirmed or refuted such speculation, without regard to its plausibility. For instance, binarity has been found where it was perhaps least expected, in Barium stars, and refuted where it could most reasonably be expected, in Wolf-Rayets. Unfortunately, many other classes of potential binaries remain without the clearest evidence of binarity, for instance Be stars, symbiotics and blue stragglers. This Advanced Study Institute was held to commemorate John Whelan (1945-1981), whose scientific career, sadly cut short in its prime, did much to further the careful study, theoretical and observational, of close binaries, as well as to encourage the spirit of international friendship and collaboration. His own interests covered a greater field, but "Interacting Binaries" seemed a reasonable restriction. We publish here 15 review talks, which still do not cover the whole topic, although they range widely.

7 Hydrodynamic Instabilities in Close Binary Systems (Frederic A. Rasio) 121 7. 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . 121 7. 1. 1 The stability of self-gravitating fluid equilibria 121 7. 1. 2 Astrophysical motivation . 123 7. 1. 3 Common envelope systems 125 7. 2 Dynamical instabilities. . . . . . . 126 7. 2. 1 Physical mechanism . . . . 126 7. 2. 2 Application to coalescing neutron star binaries 127 7. 3 Secular instabilities. . . . . . . . . . . 130 7. 3. 1 Physical mechanism . . . . . . 130 7. 3. 2 Application to contact binaries 133 8 Common Envelope Evolution in Binary Systems (Mario Livio) 141 8. 1 Introduction. . . . . . . . . . . . . . . . . . . . 141 8. 2 The entrance into the common envelope phase . . . . . 142 8. 3 The outcome of the CE phase. . . . . . . . . . . . . . . 145 8. 4 How close can we get to observing the common envelope Phase? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 8. 4. 1 How can PNe with binary nuclei be used to constrain CE physics . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 8. 4. 2 How can nova systems be used to constrain CE physics 148 8. 4. 3 Other tests of common envelope evolution 150 8. 5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 151 9 Structure and Evolution of Massive Close Binaries (Dany Vanbeveren) 155 9. 1 Introduction. . . . . . . . . . . . . . . . . . 155 9. 2 Definitions. . . . . . . . . . . . . . . . . . . 156 9. 3 Intermediate mass and massive single stars 156 9. 3. 1 Observations . . . . . . . . . . . . . 156 9. 3. 2 Stellar structure equations for non-rotating IMS's and MS's 160 9. 3. 3 Evolutionary computations of non-rotating IMS's and MS's 162 9. 3. 4 Overall comparison with observations '" 163 9. 3. 5 The role of rotation in single star evolution . . .

A small country builds a world-class telescope in its backyard and lives happily ever after (or at least for a quarter century). That in a nutshell is the story told in this collection of essays. The country of course is the Netherlands, and the telescope is the Westerbork Synthesis Radio Tele scope (WSRT), brainchild of Jan Oort. Living happily in this context is a continuing record of discovery and as such also a continuing basis for se curing observing time on facilities in other countries and operating at other frequencies. As our community celebrates the Silver Anniversary of the radio tele scope at Westerbork, it is fitting that we pause to take account of the scientific discoveries and insights it made possible. Initially the instrument represented the very significant step away from university-run, specialist facilities to a well-supported, common-user radio imager also having spec tral and polarization capabilities. It pioneered the mode of operation now common for satellite observatories, in which data is taken and calibrated by technicians and provided to researchers ready for analysis. It has been a major source of discovery in, among other areas, research on neutral hy drogen and studies of dark matter in galaxies.

The visible universe is a small perturbation on the material universe. Zwicky and Sinclair Smith in the 1930s gave evidence of invisible mass in the Coma and Virgo Clusters of Galaxies. Better optical data has only served to confound their critics and the X-ray data confirms that the gravitational potentials are many times larger than those predicted on the basis of the observed stars. Dynamical analyses of individual galaxies have found that significant extra mass is needed to explain their rotational velocities. On much larger scales, tens of megaparsecs, there is suggestive evidence that there is even more mass per unit luminosity. What is this non-luminous stuff of which the universe is made'? How much of it is there? Need there be only one kind of stuff? There are three basic possi bili ties:- all of it is ordinary (baryonic) matter, all of it is some other kind of (non-baryonic) matter, or some of it is baryonic and some is non-baryonic.

The International Heidelberg Workshop on TeV Gamma-Ray Astrophysics' brought together astrophysicists from the various fields which play a role in the formation of high energy gamma-ray emission. In particular, theoretical and observational aspects of the physics and astrophysics of pulsars and quasars, the acceleration of particles at Supernova Remnants and other strong astrophysical shock fronts, and cascade processes in universal background photon fields were comprehensively discussed in more than thirty reviews by leading experts. In their entirety these reviews describe the birth of a new field of astronomy. This field concerns cosmic gamma-rays of very high energy which are observed with ground-based optical telescopes due to the Cherenkov emission of the secondary particles created by the interaction of these gamma-rays with atoms in the Earth's atmosphere. Beyond that, the workshop encompassed the latest developments and trends in theory and observation of cosmic gamma-ray sources of all energies, from nuclear gamma-ray lines in the MeV-region, through the Bremsstrahlung, Inverse Compton, and pion decay continuum emission, to gamma-rays due the decay of exotic relics from the early Universe. Audience: Specialists as well as students in physics and astrophysics and young research workers.

An Advanced Research Workshop on Very High Energy Gamma Ray Astronomy and Related Topics was held at Durham, England during August 11-15 1986. The meeting was sponsored by the Scientific Affairs Division of NATO and the University of Durham. It is four years since the first Workshop dedicated to High Energy Gamma Ray Astronomy was held at Ootacamund, India. At that meeting the developments in Very High Energy Gamma Ray Astronomy over a period of more than 20 years were reported and the methodology, limitations, improvements and prospects for further progess were discussed. The possible requirement for a follow-up meeting was clear if the optimistic future foreseen for the field at the Ooty meeting was correct. The Durham meeting was suggested to fill this role. Although the arrangements for the Durham meeting were discussed as long ago as 1983 with possible dates in 1984 or 1986, the eventual date in 1986 has proved admirable and has coincided with a time when further advances have been reported. An important feature of the proposal for the Durham meeting was the emphasis on a series of Workshop sessions, the conclusions of each to be summarized by a Rapporteur. The purpose of these sessions was to provide a consensus view of many of the important areas in the field at a time of increasing interest by the rest of the astrophysics community.

For every astronomical topic that I have approached there has turned out to be a broader realm of possibilities than is commonly accepted or acknowledged. The "excursions" of this book are the examples. They mostly depart from the mainstream of conventional wisdom to offer a wider perspective with opportunities for further research. While my intent is to supplement that mainstream, the effect may appear to dismiss rather than to reconsider accepted tenets. Ample praise and credit for those accomplishments are already available in textbooks. Readers may very well disagree with some of the notions presented in these excursions, but I hope that they will pause long enough to evaluate the scientific basis for any disagreement. For the most part, these excursions remain incomplete and unfulfilled, yet they contain many ideas that are not available elsewhere. Whether these ideas are per ceived as a collection of unproven claims or as a storehouse of fresh opportunities will depend entirely on the attitude of the reader. The excursions do cover a rather wide span of disciplines, and that may lead to an unfocused overall impression. My hope is thereby to attract a broader audience than that of a single discipline, and to expose them to neighboring disciplines. The excursions all do have the common thread of optical science related to astronomy."

During the past years, a number of international astronomical conferences were held at the Remeis-Observatory in Bamberg, four of them sponsored by the International Astronomical Union. The first meeting was organized in 1959 and dealt with Variable Stars, the last one was held in 1981 and focussed on 'Binary and Multiple Stars as Tracers of Stellar Evolution'. The present conference was organized to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel, who was born in Minden on July 22, 1784, and died in Konigsberg on March 17, 1846. When the plan for an international conference on astrometric binaries was presented to several colleagues, we received enthusiastic support and decided to pursue the idea. A Scientific Organizing Committee was soon established, consisting of: Z. Kopal Manchester, u.K. S. M. Gong Nanjing, China (Chairman) M. Grewing Tiibingen, F.R.G. V. Abalakin Pulkovo, U.S.S.R. P. v. d. Kamp Amsterdam, Netherlands J. Dommanget Uccle, Belgium M. Kitamura Tokyo, Japan M. G. Fracastoro Torino, Italy J. Rahe Bamberg, F.R.G. W. Fricke Heidelberg, F.R.G. Ya. Yatskiv Kiev, U.S.S.R. E. H. Geyer Bonn, F.R.G. The meeting took place in Bamberg at the Remeis-Observatory, Astronomical Institute of the University Erlangen-Nurnberg, from June l3 to 15, 1984. The following institutions generously supported the meeting: Deutsche Forschungs- gemeinschaft, Bonn; Stadt Bamberg; Universitat Bamberg; Universitat Erlangen- Nurnberg; University of Manchester.

Fundamental unsolved problems of stellar astrophysics include the effects of angular momentum on stellar structure and evolution, the nature and efficiency of the processes by which angular momentum is redistributed within and lost from stars, and the role that stellar rotation plays in enhancing or driving stellar mass loss. There appears to be a qualitative change in the nature and efficiency of these mechanisms near spectral type FO: hotter (more massive) stars typically retain more angular momentum at least until they reach the main sequence, while cooler stars typically spin down quickly. For the hotter stars, recent work suggests a strong link between the type of pulsation behavior, the mass loss rates, and the rotation velocity. If the same mechanisms are able to drive mass loss from the main sequence A stars, as has recently been proposed, then the current interpretations of a number of observations will be drastically affected: e. g. the ages of clusters may be incorrect by up to a factor of two, and the surface abundances of isotopes of He, Li and Be may no longer give constraints on cosmological nucleosynthesis. There are also effects on the evolution of the abundances of elements in the interstellar medium and on the general evolution of populations of stars. Thus the questions of the mechanisms of angular momentum and mass loss of stars more massive than the sun is important not only for stellar studies but for the foundations of much of modern astrophysics.

Understanding the formation of objects at all scales in the universe, from galaxy clusters to stars and planets, is a major problem in modern astrophysics, and one of the most exciting challenges of twenty-first century astronomy. Even though they are characterized by different scales, the formation of planets, stars and galaxies share many common physical processes and are rooted in the same underlying domains of physics. This unique reference for graduate students and researchers in astrophysics is the first to cover structure formation on various scales in one volume. This book gathers together extensive reviews written by world experts in physics and astrophysics working in planet, star and galaxy formation, and related subjects. It addresses current issues in these fields and describes the recent observational status and state-of-the-art theoretical and numerical methods aimed at understanding these problems.

Eclipses and problems related to them have been, from ancient times, one of the main interests not only of astronomers but indeed of all mankind. The appearance of eclipses, lunar as well as solar, excited the imagination of our ancestors and provoked their curiosity to explain their origin or to use them for the further investigation of celestial bodies. With the present development of astronomy the eclipse problems are not limited to the Sun and the Moon, as in the past, but have been progressively extended to the components of the solar system and to domains of radiations other than optical ones. Our intention is to give an account of all these problems in their theoretical and experimental form with some additions on their historical development. Those of our readers not interested in the historical side may feel at first inclined to ignore this part, but we are sure that eventually they will be sufficiently interested to repair this omission.

This workshop is devoted to Double stars. The general topics of the meeting were: for mation, dynamics and evolutionary tracks. In accordance with the pure tradition of the Saint James way, "pilgrims" from all over the world come to meet together in Santiago. Although with a common interest (double stars), this meeting was a multidisciplinary one, since scientists with different backgrounds participated in it. As a matter of fact, we think that this is the first workshop jointly supported by IAU Commissions 7 (Celestial mechanics) and 26 (Double and multiple stars). It is our belief that this meeting will be the origin of a more close relations and common research. This meeting was held under the invitation of the University of Santiago de Compostela to commemorate its fifth centenary, and organized by the Astronomical Observatory named after its founder, Ramon M. Aller, who made significant contributions in the study of visual double stars, and was one of the pioneers who put the seeds of the present blossoming of Astronomy in Spain. The Scientific Organizing Committee was formed by Drs. C. Allen, P. Couteau, J. A. Docobo, R. Dvorak, A. Elipe, S. Ferraz-Mello (co-chairman), H.A.McAlister, M. Valtonen, C.Worley (chairman) and H. Zinnecker. The Local Organizing Committee was formed by Drs. J. A. Docobo (chairman), A.

edited by c. H. Lineweaver, J. G. Bartlett, A. Blanchard Observatoire Astronomique de Strasbourg, Strasbourg, France M. Signore Ecole normale superieure, Paris, France and J. Silk Departments of Astronomy and Physics, University of California at Berkeley, Berkeley, CA, U. S. A. Kluwer Academic Publishers Dordrecht / Boston / London Published in cooperation with NATO Scientific Affairs Division ISBN-13:978-94-010-6512-2 e-ISBN-13:978-94-009-0051-6 DOI:10. 107/ 978-94-009-0051-6 Softcover reprint of the hardcover 1st edition 1997 Dedication We dedicate these proceedings to the people who paid for it: taxpayers of the NATO alliance. Table of Contents PREFACE IX LIST OF PARTICIPANTS XI LISTOF CONTRIBUTORS Xlll I. Introduction, Mathematical Tools and Background An Introduction to CBR Studies: Spectrum, Degree-Scale Fluctuations, Foregrounds and Interferometry R. B. Partridge ElementsofGeneral Relativity, Cosmology and the Cosmic Microwave Background Jose L. Sanz 33 Statisticsand Random Functions in Astrophysics BernhardIT. Jones 67 Structure Formation Joseph Silk III II. eMB Anistropies CalculationofCosmic Background Radiation Anisotropies and Implications Emory F. Bunn 135 The CMB Anistropy Experiments: Cosmic Microwave Background George F. Smoot 185 viii III. CMB Spectrum The CMBR-Spectrum: ATheoretical Introduction Albert Stebbins 241 The CMB Spectrum George F. Smoot 271 IV. Astroparticle Physics Inflation and the Cosmic Background Radiation: What Every Cosmologist Needs to Know Michael S. Turner 309 Primordial Chemistry and Cosmic Background Radiation M. Signori, P. Encrenaz, R. MaoJi, B. Melchiorri, F. Melchiorri and D. Puy 345 The Cosmic Background Radiation and Elementary Particles Pierre Salati 365 V.

Based on the lecture notes of a school titled 'Tides in Astronomy and Astrophysics' that brought together students and researchers, this book focuses on the fundamental theories of tides at different scales of the universe-from tiny satellites to whole galaxies-and on the most recent developments. It also attempts to place the study of tides in a historical perspective. Starting with a general tutorial on tides, the theme of tides is approached in 9 chapters from many directions. They allow non-experts to pick up a physical intuition and a sense of orders of magnitude in the theory of tides. These carefully prepared lecture notes by leaders in the field include many illustrative figures and drawings. Some even offer a variety of simple back-of the-envelope problems.