volume XIX A of IAU Transactions contains the reports by Presidents of Commissions, covering the period July 1981 - June 1984. The topics of IAU Commissions deal with all of contemporary astronomy and the present volume therefore constitutes an exhaustive and unique record of astronomical research during this interval. It is particularly useful for astronomers and other scientists who want to gain an overview of a certain field, not necessarily near their own research area. Each Commission President was requested, by early 1984, to begin prep arations for the compilation of his/her Commission report. All members of Commissions were asked to supply details about their individual research pro grammes. The ensuing, very substantial task of concatenating was undertaken in late 1984 by the Presidents, often supported by a team of authors, all recog nized authorities in their fields. In order to preserve some measure of uni formity - which is in any case very difficult with so many authors - editorial guidelines were sent to Presidents, including the number of pages allotted to each Commission.

Since the previous Symposium, several exciting new developments and advances have occurred in the field of frequency standards and metrology. These include the first results on the long-tenn stability of a millisecond Pulsar, for which data 14 integrated over several years now show a stability of around 10- . Improvements in the understanding of various biases in Cesium beam standards promise accuracies in the low 14s for primary standards and in the low 13s for short commercial tubes, for which long tenn stabilities in low 14s have already been shown to be obtainable by accuracy improvement. Beams using optical pumping for state selection and for detection have been operated with excellent results, and more are being realized. Other new frequency standards which have appeared include a macroscopic rf trap with Mercury ions, which perfonns in the low 15s in one day, the sub millimeter metastable Magnesium beam, which has shown a short tenn stability 19 in the low 12s in one second and promises an accuracy of 10- , and the cold Hydrogen masers, which have such high stabilities that they cannot be measured with existing local oscillators. Prospects for future developments include laser manipulation of neutrals and spectroscopy of single ions at rest in a trap. Both these groups of techniques have great potential for unprecedented accuracy and short-and long-tenn stability, and new superior frequency standards are expected to be realizable in this way in the not too distant future.

Distinguished authors discuss topics in physical oceano- graphy, transonic aerodynamics, dynamics of vorticity, numerical simulation of turbulent flows, astrophysical jets, strange attractors, human-powered flight, and thefluid mechanics of the Old Faithful geyser and of the Mount St. Helens eruption of 1980. The authors deal with specific problems, but the emphasis is usually on the way that re- search is carried out at the edge of understanding, and often on the role of new techniques, instruments, and re- search strategies.

Mary Somerville (1780-1872), after whom Somerville College Oxford was named, was the first woman scientist to win an international reputation entirely in her own right, rather than through association with a scientific brother or father. She was active in astronomy, one of the most demanding areas of science of the day, and flourished in the unique British tradition of Grand Amateurs, who paid their own way and were not affiliated with any academic institution. Mary Somerville was to science what Jane Austen was to literature and Frances Trollope to travel writing. Allan Chapman's vivid account brings to light the story of an exceptional woman, whose achievements in a field dominated by men deserve to be very widely known.

Many important observational clues about our understanding of how stars and planets form in the interior of molecular clouds have been amassed using recent technological developments. ESO's very large telescope promises to be a major step forward in the investigation of stellar nurseries and infant stars. This volume collects papers from the leaders in this very timely field of astrophysical research. It presents theoretical and a host of observational results and many papers show the plans for future observations.

The contributions in this volume report recent studies on the sun and late-type stars. Particular emphasis is placed on observations that are relevant to the question of large-scale magnetic activity, and also on the theoretical (dynamo) models for such activity. Experimental papers deal with surface imaging techniques. Explicit computer simulations of hydromagnetic turbulence give insight into the magnetic topology and associated fluid motions, especially near the base of the convection zone. In addition, mean-field dynamo models are presented. The book addresses researchers but should also AEjbe useful for graduate students.

The articles in this book deal with energetic hadron processes near astrophysical compact objects, including compact binary systems and active galactic nuclei. A variety of observational results suggest that relativistic hadrons can be produced in the vicinity of these objects. Amongthe topics treated in detail are the question whether a large fraction of the energy produced by active galactic nuclei is channeled into a population of relativistic protons and the problem of the origin of very high and ultra-high energy gamma rays from galactic compact sources.

The book reviews methods for the analysis of astronomical datasets, particularly emphasizing very large databases arising from both existing and forthcoming projects, as well as current large-scale computer simulation studies. Leading experts give overviews of cutting-edge methods applicable in the area of astronomical data mining.

When leaving the Victoria airport the day before our Colloquium, I saw a van of the Dunsmuir Lodge marked with big letters which I read as "Alcohol Colloquium". I do often make such blunders because of the global, casual, and careless way in which I read various ads, and checked myself quickly to read it correctly as "Algol Colloquium". Millions of fellow citizens could easily make the same mistake, and no apology could be expected. Even I read and hear the word alcohol more frequently than Algol, although I must say that Algols have given me more pleasure and fewer headaches over the years; in that, however, I may be a singularity, and possibly a pitiful one at that. Being appointed Chairman of the Scientific Organizing Committee, I may be deemed to be a purer" Algolist" than other investigators, although my range of active interests is much broader; and the same is true about all the 28 invited speakers and all the other participants of the Colloquium. Our interest are strongly diversified, but there are several good reasons that brought us together at this Colloquium.

The book reviews the knowledge obtained from ground-based and space-borne solar flare research thus at the same time preparing for the forthcoming mission of the satellite Solar A which will be launched in 1991. Accordinglyone section is devoted to experiments on Solar A. The rest review both theory and observational facts to give a physically realistic picture of flares, including problems of magnetic flux emergence, high energy particles in flares, heating and flows in flares, and further problems of solar activity.

This is a definitive reference of 2,100 fundamental formulae used in astronomy and astrophysics. It not only makes accessible all the indispensable equations employed in the field, but also carefully explains the physical assumptions and constants underlying them. The bibliography contains more than 1,900 citations of original papers. Accounting for nearly 20 years since the previous edition, this volume is significantly revised and expanded.

These workshop proceedings aim to provide a broad overview of recent developments in the study of hot stars, both from the observational and the theoretical point of view. Included are first results from the Hubble Space Telescope and ROSAT, the effects of non-radial pulsations, mass loss, magnetic fields, and diffusion, as well as modern theoretical methods to treat radiative transfer and compute model atmospheres. Many new results are described, including the discovery of a B star in the halo of M31. Together the reviews provide a general overview of hot-star spectroscopy suitable for preparing advanced lecture courses and as an introductory text for graduate students.

This book provides an introduction to the theory of relativity and the mathematics used in its processes. Three elements of the book make it stand apart from previously published books on the theory of relativity. First, the book starts at a lower mathematical level than standard books with tensor calculus of sufficient maturity to make it possible to give detailed calculations of relativistic predictions of practical experiments. Self-contained introductions are given, for example vector calculus, differential calculus and integrations. Second, in-between calculations have been included, making it possible for the non-technical reader to follow step-by-step calculations. Thirdly, the conceptual development is gradual and rigorous in order to provide the inexperienced reader with a philosophically satisfying understanding of the theory. The goal of this book is to provide the reader with a sound conceptual understanding of both the special and general theories of relativity, and gain an insight into how the mathematics of the theory can be utilized to calculate relativistic effects.

Jupiter's ice moon Europa is widely regarded as the most likely place to find extraterrestrial life. This book tells the engaging story of Europa, the oceanic moon. It features a large number of stunning images of the ocean moon's surface, clearly displaying the spectacular crack patterns, extensive rifts and ridges, and refrozen pools of exposed water filled with rafts of displaced ice. Coverage also features firsthand accounts of Galileo's mission to Jupiter and its moons. The book tells the rough and tumble inside story of a very human enterprise in science that lead to the discovery of a fantastic new world that might well harbor life.

The joint NASA-ESA Cassini-Huygens mission promises to return four (and possibly more) years of unparalleled scientific data from the solar system's most exotic planet, the ringed, gas giant, Saturn. Larger than Galileo with a much greater communication bandwidth, Cassini can accomplish in a single flyby what Galileo returned in a series of passes. Cassini explores the Saturn environment in three dimensions, using gravity assists to climb out of the equatorial plane to look down on the rings from above, to image the aurora and to study polar magnetospheric processes such as field-aligned currents. Since the radiation belt particle fluxes are much more benign than those at Jupiter, Cassini can more safely explore the inner regions of the magnetosphere. The spacecraft approaches the planet closer than Galileo could, and explores the inner moons and the rings much more thoroughly than was possible at Jupiter. This book is the second volume, in a three volume set, that describes the Cassini/Huygens mission. This volume describes the in situ investigations on the Cassini orbiter: plasma spectrometer, ion and neutral mass spectrometer, energetic charged and neutral particle spectrometer, magnetometer, radio and plasma wave spectrometer and the cosmic dust analyzer. This book is of interest to all potential users of the Cassini-Huygens data, to those who wish to learn about the planned scientific return from the Cassini-Huygens mission and those curious about the processes occurring on this most fascinating planet. A third volume describes the remote sensing investigations on the orbiter.

17 readable articles give a thorough and self-contained overview of recent developments in relativistic gravity research. The subjects covered are: gravitational lensing, the general relativistic n-body problem, observable effects in the solar system, gravitational waves and their interferometric detection, very-long-baseline interferometry, international atomic time, lunar laser- ranging measurements, measurement ofthe gravitomagnetic field of the Earth, fermion and boson stars and black holes with hair, rapidly rotating neutron stars, matter wave interferometry, and the laboratory test of Newton's law of gravity.Any scientist interested in experimentally or observatio- nally oriented relativistic gravity will read the book with profit. In addition, it is perfectly suited as a complementary text for courses on general relativity and relativistic astrophysics.

Observations with X-ray satellite ROSAT over the past 5 years have established supersoft X-ray sources as a new class of objects in our Galaxy and beyond. Optical follow-up observations have revealed the binary nature of several of them. Recent population synthesis calculations have shown that the number of such binaries is expected to be considerably larger than those of the common low- and high-mass X-ray binaries. This book provides the first comprehensive overview of the many recent observational discoveries and theoretical investigations. It describes relations between supersoft sources and other areas in astrophysics. This volume also comprises a complete catalog of presently known supersoft sources including a comprehensive bibliography of observational results.

This book contains the contributed papers and reviews from IAU Colloquium Number 114 on White Dwarfs held at Dartmouth College in August 1988. All the current fields of research in this area are covered including the evolution of white dwarfs, links to progenitors, luminosity functions of white dwarfs, evolution of white dwarfs in binaries, spectroscopy and atmospheric abundances, diffusion, accretion and convective mixing, the mass-radius relation, gravitational redshifts, masses of white dwarfs, and magnetic white dwarfs. Special emphasis has been placed on the intrinsic properties of single white dwarfs. All the articles are by internationally known authorities and contain the most up-to-date information available at the time of writing.

This collection of papers presents a rather complete review of current knowledge of hot spots in some strong extragalactic radio sources. An overview of known results along with new data on radio observations and optical observations is given in the first and second parts of the book. Recent computational techniques which allow modelling and simulations of hot spots and jet behaviour are presented in the third part. The fourth part discusses particle acceleration and shock front phenomena. The articles will help the reader to appreciate the role hot spots play as laboratories for studying the interaction of jets with the surrounding medium and for testing our understanding of the overall source dynamics. The book is a valuable complement to the existing literature and an excellent introduction to this fairly new field of research.

The idea of a joint ESO / Australia meeting on the large number of exciting new facilities that are, or will soon be, available tihne southern hemisphere arose quite naturally. In the optical and the near-infrared, the Very Large Telescope (VLT) will soon be operational. In the radio, the Australia Telescope Com pact Array is going to be upgraded to higher frequencies (20 and 100 GHz), together with an improvement in very long baseline interferometry (VLBI) facil ities. Other major facilities, such as the Large Millimetre Array and the lkT are being planned. Moreover, new deep surveys are underway in the southern hemi sphere: the southern Hubble Deep Field, the ESO Imaging Survey (BIS), pan oramic deep surveys with the UK Schmidt telescope, and the Anglo-Australian Telescope (AAT) 2dF galaxy/QSO redshift survey in the optical; and the Parkes multibeam HI survey and Molonglo Observatory Synthesis Telescope (MOST) Wide Field continuum survey at radio wavelengths. With all these new facilities, important progress will be made regarding important issues such as the large scale structure of the universe, the very early universe and the associated first epoch of galaxy formation. The generation of large databases, and the oppor tunity for sensitive follow-up observations in complementary wavebands, mean that coordinated radio, infrared and optical projects in the southern hemisphere are likely to become increasingly attractive and important.

Extinction and standardization corrections to infrared measurements are of the utmost importance in astronomy. Various views on these concepts and problems of implementation in infrared photometry are discussed thoroughly and recommendations are presented. Among these are: the adoption of narrower broad-band "Johnson" filters that are better centered in the atmospheric water windows than is currently the case; the measurements of atmospheric water vapor content concurrent with the astronomical measurements; the use of appropriate atmospheric models to treat the extinction adequately; and the publication of complete details of the systemic passbands and their transformability to other systems. To conclude the volume, R. Bell summarizes and comments on the contributions to the symposium, and the editor adds a concluding postscript on post-meeting developments and perspectives.

Cosmology has dramatically evolved during the last decade and there has been vast development of, e.g., theories of galaxy formation in connection with the early universe or gravitational lensing. These new developments motivated the editors to organize a school covering all of these ideas and observations in a pedagogical way. The topics covered in the 26 lectures of this summer school include: QSO absorption systems, identification of objects at high redshift, radiogalaxies, galaxy formation and evolution, galaxy number counts, clustering, theories of structure formation, large-scale structure and streaming motions, gravitational lensing, and spectrum and anisotropies of the cosmic microwave background radiation. Observational developments, data analysis, and theoretical aspects are equally treated.

From June 7-9, 1995, the European Southern Observatory (ESO) and the Max Plank Institut fiir Astrophysik (MPA) jointly held the Workshop on Spiral Galaxies in the Near-IR. This meeting took place at the ESO headquarters in Garching bei Miinchen, Germany. The weather waschanging, with the biergarten closed, but that did not stop 85 people from allover the world from attending the meeting. The three days were intensive, with talks and coffee and posters from 9 am to 6 pm, and very productive indeed for everyone. The topics covered the stellar populations of the Milky Way and other more distant spirals, the role of dust, the dynamics of spiral galaxies, and the nuclear activity seen at near-IR wavelengths. This volume presents the original contributions from the participants, including several papers that review the state-of-the-art knowledge in these various subjects. The editors would like to thank first and foremost Christina Stoffer, for she took care of everything. The meeting would not have been so successful without her expertise and efficiency. We are deeply indebted to the directors of MPA and ESO Science, Simon White and Jacqueline Bergeron, for their support and encouragement. We would also like to thank the other members of the scientific organizing committee: R. Genzel, K. Freeman, A. Moorwood, S. White, M. Rieke and E. Athannasoula, for their advice with the organization of the program. We also thank G. Rieke, R. Genzel, L. Athannasoula, A. Renzini and R.

There is abundant evidence that essentially all luminous hot-star winds contain time-dependent and anisotropic structures. IAU Colloquium 169 was convened to review the observations of variability and asphericity, to discuss the physical processes that might cause such behavior and to look for evolutionary consequences. The topics included OBA stars, Be stars, Wolf-Rayet stars, Be stars, and luminous blue variables (LBVs). The role played by rotation in shaping the stellar wind was a recurrent theme. Photospheric pulsations and/or magnetic fields are particularly appealing mechanisms for triggering the formation of recurrent wind structures.

The same kind of physics is frequently common to very different fields of Astrophysics, so experts in each of these fields have often much to learn from each others. It was therefore logical that the International Astronomical Union should sponsor a colloquium about an ion which pro duces many spectral lines that can be used as a diagnostic for many sorts of objects, and which may sometimes have a major influence on physical processes occurring in astro physical sources. The lines of singly ionized iron (FeII) are present in absorption and emission in the spectra of objects such as the Sun, cool stars, circumstellar envelopes of hot stars, novae, diffuse nebulae including the supernova remnants, and active galactic nuclei. These lines are very often formed far from LTE, and their interpretation is not easy in view of the complex Grotrian diagram for FeII, and the gaps in the knowledge of various physical parameters. In addition, the density of very strong FeII lines becomes very large in the ultraviolet, and the lines can play a major role in the line blanketing. They need therefore to be taken into account in any energy balance argument.