Pulsars are stars, a significant part of whose observed energy output is not continuous but is emitted as distinct flashes or pulses of electromagnetic radiation. Many pulsars also emit some radiation weakly and constantly, forming a background for the more intensive pulses. Three distinct classes of pulsars are presently known to astronomers, according to the source of energy that powers the radiation: Rotation-powered pulsars, where the loss of rotational energy of the star powers the radiation X-ray pulsars, where the gravitational potential energy of accreted matter is the energy source, and Magnetars, where the decay of an extremely strong magnetic field powers the radiation. Although all three classes of objects are neutron stars, their observable behaviour and the underlying physics are quite different. There are, however, connections. For example, X-ray pulsars are probably old rotation-powered pulsars that have already lost most of their energy, and have only become visible again after their binary companions expanded and began transferring matter on to the neutron star. The process of accretion can in turn transfer enough angular momentum to the neutron star to "recycle" it as a rotation-powered millisecond pulsar.

It is generally believed that most of the matter in the universe is dark, i.e. cannot be detected from the light which it emits (or fails to emit). Its presence is inferred indirectly from the motions of astronomical objects, specifically stellar, galactic, and galaxy cluster/supercluster observations. It is also required in order to enable gravity to amplify the small fluctuations in the cosmic microwave background enough to form the large-scale structures that we see in the universe today. For each of the stellar, galactic, and galaxy cluster/supercluster observations the basic principle is that if we measure velocities in some region, then there has to be enough mass there for gravity to stop all the objects flying apart. Dark matter has important consequences for the evolution of the Universe and the structure within it. According to general relativity, the Universe must conform to one of three possible types: open, flat, or closed. The total amount of mass and energy in the universe determines which of the three possibilities applies to the Universe. In the case of an open Universe, the total mass and energy density (denoted by the Greek letter Omega) is less than unity. If the Universe is closed, Omega is greater than unity. For the case where Omega is exactly equal to one the Universe is "flat". This book details leading-edge research from around the globe.

Thoroughly revised, expanded and updated throughout, this new edition of Astrophysics of GaseousNebulae and Active Galactic Nuclei is a graduate-level text and reference book on gaseous nebulae, nova and supernova remnants, and the emission-line regions in Seyfert galaxies, radio galaxies, quasars, and other types of active galactic nuclei. Much of the new data and many of the new images are from the Hubble Space Telescope and some of the largest ground-based telescopes in the world. Two wholly new chapters have been added, one on infrared astronomy and the other on X-ray astronomy, reflecting the great advances in these fields. This new edition also contains two completely new appendices, one a long primer on the quantum-mechanical concepts used in the analysis of nebular emission-line spectra, and the other a briefer description of molecular spectra. Large amounts of new data on dust in nebulae and quasars, and the photo-dissociated regions containing neutral atoms, molecules, and dust within and around them, have also been added to the book. Thus, the previous edition of this classic text, which has been tried, tested, and widely used for thirty years, has now been succeeded by a new, revised, updated, larger edition, which will be valuable to anyone seriously interested in astrophysics.

Clusters of Galaxies & Extragalactic Radio Sources

What force do the Big Bang, the expansion of the Universe, dark matter and dark energy, black holes, and gravitational waves all have in common? This book uncovers gravity as a key to understanding these fascinating phenomena that have so captivated public interest in recent years. Readers will discover the latest findings on how this familiar force in our everyday lives powers the most colossal changes in the Universe. Written by the widely recognized French public scientist and leading astrophysicist Pierre Binetruy, the book also explains the recent experimental confirmation of the existence of gravitational waves.

Our understanding of the formation of stars and planetary systems has changed greatly since the first edition of this book was published. This new edition has been thoroughly updated, and now includes material on molecular clouds, binaries, star clusters and the stellar initial mass function (IMF), disk evolution and planet formation. This book provides a comprehensive picture of the formation of stars and planetary systems, from their beginnings in cold clouds of molecular gas to their emergence as new suns with planet-forming disks. At each stage gravity induces an inward accretion of mass, and this is a central theme for the book. The author brings together current observations, rigorous treatments of the relevant astrophysics, and 150 illustrations, to clarify the sequence of events in star and planet formation. It is a comprehensive account of the underlying physical processes of accretion for graduate students and researchers.

The numbers involved when it comes to discussing stars, galaxies and the inconceivably vast tracts of empty space between them are staggering. With hundreds of billions of galaxies in the observable universe, all of varying shapes, sizes and ages - each containing hundreds of billions of suns - at first glance our universe appears frustratingly unknowable, and yet it is captivating to explore. As a species we have only recently come to appreciate that our Milky Way is just one of myriad galaxies spread throughout the universe, with modern scientific breakthroughs forcing dramatic re-evaluations of our place in the immense cosmos. Our knowledge is growing daily and the pace of research continues to accelerate but we are still far away from from a complete understanding of how the galaxies came to be, and the processes that shaped them. Written by an active researcher in the field, Galaxy: Mapping the Cosmos tells the rich scientific story of galaxy evolution and observation - discoveries of 'spiral nebulae', the nature of galaxies and the current 'World Model'.Astronomer James Geach takes us on a tour of what is currently known and unknown, discussing why the ancient science of astronomy continues to fascinate humanity. Appealing to all readers interested in astronomy and cosmology, and featuring 100 colour illustrations, Galaxy explores the enigma of our cosmic habitat, chronicling how our home in the universe came to be.

In less than a century, the accepted picture of the universe transformed from a stagnant place, composed entirely of our own Milky Way galaxy, to a realm inhabited by billions of individual galaxies, hurtling away from one another. We must thank, in part, Edwin P. Hubble, one of the greatest observational astronomers of the 20th century. In 1936, Hubble described his principal observations and conclusions in "The Realm of the Nebulae," which quickly became a classic work. Two new introductory pieces, by Robert P. Kirshner and Sean M. Carroll, explain advances since Hubble's time and his work's foundational importance.
"Meaningful, historically accurate, and thoroughly delightful reading."--Gail O. Clark, "Astronomy"

In the 42 years that Edward Pickering directed the Harvard College Observatory, he and his team of women "computers" made strides in promoting the new field of astrophotography, discovered the first spectroscopic binary star system, and cataloged more than 225,000 stars. Pickering hired women such as Henrietta Leavitt, who found a way to measure the distances to faraway stars, and Cecilia Payne-Gaposchkin, whose later work became the foundation for astrophysics, to process astronomical data gathered at the observatory. The advances these women made under Pickering's direction broadened the window of professional opportunity for women as well as our greater understanding of the universe. This new title highlights the lives of Pickering and his women "computers."

The interstellar medium (or ISM) is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. This book presents topical research in the study of interstellar medium, including explosive processes in the interstellar medium as sources of ultrahigh-energy cosmic rays; heteronuclear diatomics in diffuse and translucent clouds; far ultraviolet observations of the Large Magellanic Cloud; MDH simulations of Parker instability undergoing cosmic-ray diffusion; deuterium in the interstellar medium and interaction of planetary nebulae, Eta-Carinae and supernova remnants with the interstellar medium.

Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A black hole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesised that the most massive galaxies in the universe -- "elliptical galaxies" -- grow simultaneously with the supermassive black holes at their centres, giving us much stronger evidence that black holes control galaxy formation. This book reviews new evidence in the field.

This book provides a comprehensive, self-contained introduction to one of the most exciting frontiers in astrophysics today: the quest to understand how the oldest and most distant galaxies in our universe first formed. Until now, most research on this question has been theoretical, but the next few years will bring about a new generation of large telescopes that promise to supply a flood of data about the infant universe during its first billion years after the big bang. This book bridges the gap between theory and observation. It is an invaluable reference for students and researchers on early galaxies.

"The First Galaxies in the Universe" starts from basic physical principles before moving on to more advanced material. Topics include the gravitational growth of structure, the intergalactic medium, the formation and evolution of the first stars and black holes, feedback and galaxy evolution, reionization, 21-cm cosmology, and more. Provides a comprehensive introduction to this exciting frontier in astrophysics Begins from first principles Covers advanced topics such as the first stars and 21-cm cosmology Prepares students for research using the next generation of large telescopes Discusses many open questions to be explored in the coming decade

IAU Symposium 356 summarises the most recent results in the field of active galaxies and active galactic nuclei (AGN). These are some of the most luminous sources in the Universe, also the most distant ones that we can observe, so they are very important for understanding the early Universe and its evolution through cosmic time. This volume gives an overview of the current status in the field of active galaxies including: AGN multiwavelength observations; different AGN types and their properties; AGN variability; active supermassive black holes and properties of galaxies in which they reside; triggering, feedback and shutting off AGN activity; relativistic jets and environments of active galaxies; and AGN evolution. IAU S356 was the third IAU symposium organised in Africa in the past 100 years since the IAU was established, and the first one organised in Ethiopia, highlighting current developments in astronomical research in Africa.

The New General Catalogue (NCG), originally created in 1888, is the source for referencing bright nebulae and star clusters, both in professional and amateur astronomy. With 7840 entries, it is the most-used historical catalogue of observational astronomy, and NGC numbers are commonly used today. However, the fascinating history of the discovery, observation, description and cataloguing of nebulae and star clusters in the nineteenth century has largely gone untold, until now. This well-researched book is the first comprehensive historical study of the NGC, and is an important resource to all those with an interest in the history of modern astronomy and visual deep-sky observing. It covers the people, observatories, instruments and methods involved in nineteenth-century visual deep-sky observing, as well as prominent deep-sky objects. The book also compares the NGC to modern object data, demonstrating how important the NGC is in observational astronomy today.

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.

Every 5 years since 1967 a meeting has been held to discuss the subject of planetary nebulae and their central stars. Previous meetings have been held in Tatranska Lomnica (Czechoslovakia); Liege (Belgium); Ithaca, New York (U. S. A); and London (Great Britain). IAU Symposium 131 was sponsored by IAU Commision 34, on Interstellar Matter and co-sponsored by IAU Commisions 35 and 36 on Stellar Constitution and Theory of Stellar Atmospheres. The symposium was held at the Universidad Nacional Autonoma de Mexico in Mexico City, October 5-9, 1987. It took place in one of the old buildings of the University of Mexico in the downtown area. The inner patio of the building provided very pleasant surroundings for the poster sessions and for extensive discussions among the participants. The meeting was attended by 160 scientists from 22 countries. The Scientific Organizing Committee,under the chairmanship of J.B. Kaler, prepared a comprehensive scientific program based on a set of invited presentations. All contributed papers were presented in poster form. The Scientific Organizing Committee would like to thank the staff of the University of Illinois Department of Astronomy: Dr. Ron Allen for granting financial support; Carol Stickrod, Louise Browning, Deana Griffin and Sandie Osterbur for their help with the organization. IAU provided economic assistance to a group of young astronomers.

This volume is the documentation of the second Course on 'Neutron Stars, Active Galactic Nuclei and Jets', held at Erice in September 1988. This second Course was devoted to our knowledge about neutron-star sources. The poster spoke of: pulsars, accreting X-ray sources and jet englnes, perhaps also UHE pulsars, X­ ra~' bursters and black-hole candidat.es. Neutron stars have even been proposed as the primary cosmic-ray boosters. Most of theil' properties are stil1 controversial, such as their birth mechanism (neutrino versus magnetic piston), internal structure (neutrons, quarks, strange particles), magnetic, thermal and spin histories, wind generation (hydrogen versus pair plasma, radiation versus centrifugal pressure), magnetospheric structure and accretion modes (along field lines versus quasi-Keplerian). The listed controversies have largely survived through the Course and entered into the proceedings. Several lecturers speak of 'magnetic-field decay' in neutron stars, of the 'recycling' of old pulsars, and of 'accretion-induced collapse' of white dwarfs as though such processes were textbook knowledge. Terms and abbreviations like RPSR (=recycled pulsar), spinup line, AIC, and ADC (=accretion disk corona) help to foster the assumptions. It is not clear to me at this time whether any of these notions has an application to reality.

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.

What is the nature and composition of the dust grains responsible for the visual extinction in our Galaxy and in other galaxies beyond? What are the ranges in temperature of dust grains? Can these be less than 2.7K? Can the distribution of cold grains be studied optically at unprecedented arcsecond resolution? How does the presence of dust affect the morphology of a galaxy? Is this new dust-penetrated view bringing us to the verge of a breakthrough in understanding the connection between galaxy morphology and the underlying physics of galaxies? How large are the amounts of cold molecular hydrogen gas and cold dust in galactic disks? These are some of the key issues addressed in this book, which takes the postgraduate reader and professional researcher to the cutting edge of this rapidly developing field. Unique features of the book include fourteen in-depth invited review papers and twenty-six pages of discussion transcribed from a television tape. The contributions reflect the entire proceedings of an intensive one week International Conference on cold dust and galaxy morphology held in Johannesburg, South Africa, during January 1996.

EDWIN TURNER AND RACHEL WEBSTER Co-Chairs, Scientific Organizing Committee lAU Symposium 173, Astrophysical Applications of Gravitational Lenses, was held in Melbourne, Australia from July 9-14, 1995. The Symposium was sponsored by lAU Commissions 47 and 40. With the discovery by Walsh and collaborators of the first instance of a gravitational lens, the multiply imaged quasar 0957+561, the area of grav­ itational lensing moved from speculative theory to a major astrophysical tool. Since that time, there have been regular, approximately biennial in­ ternational meetings both in Europe and in North America, which have specifically focussed on gravitational lensing. On this occasion, with the blessing of the lA U, the meeting was held at the University of Melbourne in Australia. It was the first international astronomical meeting to be held at the University of Melbourne, and hope­ fully has given the astronomical community some enthusiasm for trekking half-way round the globe to Australia to discuss their latest work.

This volume is composed of four major in-depth yet pedagogic review chapters on the subject of star formation, written by the foremost researchers in the field. Recent infrared and millimeter radio observations are respectively reviewed by Charlie Lada and Phil Myers, both of Harvard-Smithsonian Center for Astrophysics. The theoretical work is reviewed by Frank Shu of UC-Berkeley on the gravitational collapse of dense cores in a giant molecular cloud to form sunlike stars and Bruce Elmegreen of IBM-Watson on the gravitational instability, leading to large-scale star formation. They have written at a level most suitable for graduate students or young researchers who want to develop their research interest in the field, with the most complete literature survey to date. This volume is not an ordinary conference proceedings, but a textbook to be used in graduate study in astrophysics. The volume also includes other short and interesting contributions from Doug Lin of UC-Santa Cruz, Paul Ho of Harvard-Smithsonian, Masa Hayashi of Tokyo University, Debra Elmegreen of Vassar, Jing-Yao Hu of Beijing Observatory, Guo-Xuan Sung of Shanghai Observatory, Chi Yuan of CCNY and ASIAA, and Wen-Ping Chen of Central University, Taiwan.