Willem Wamsteker – författare

The proceedings of the XXVIIth ESLAB symposium presents a comprehensive review of the status of astrophysics and cosmology today. The book provides an insight into the current and future fundamental problems which will be addressed by scientists in the 21st century. The accomplishments of the golden decades, in which many new observing windows have been opened to all astronomers through space exploration, the 4-metre class ground telescopes and interferometric techniques at radio wavelengths, are highlighted concisely. The state of our theoretical understanding of the Universe, extending from the nearby interstellar medium (the Solar Bubble) out to the very early stages of the Universe, and the importance of gravitational lenses are illustrated in lucid reviews. A set of colour pictures from recent experiments illustrates the future of observational astronomy.The reviews are comprehensive and are at a level suitable for professional astronomers who want to remain informed about the fields beyond their specialties, for students at graduate and undergraduate level, as well as for decision makers who need to understand the importance of the scientific challenges which will require support in the future.

When the first United Nations/European Space Agency Workshop for Basic Space Science was planned to be held in Bangalore, India (1991) on the invitation of ISRO, few of those involved could expect that a unique forum was going to be created for scientific dialogue between scientists from developing and industrialized nations. As the format of the first workshop was on purpose left free with time for presentations, working sessions, and plenary discussions, the workshop was left to find its own dynamics. After a decade of UN/ESA Workshops, this book brings together the historical activities, the plans which have been developed over the past decade in the different nations, and the results which have materialized during this time in different developing nations. It aims to achieve for development agencies to be assisted in ways to find more effective tools for the application of development aid. The last section of the book contains a guide for teachers to introduce astrophysics into university physics courses. This will be of use to teachers in many nations. Everything described in this book is the result of a truly collective effort from all involved in all UN/ESA workshops.The mutual support from the participants has helped significantly to implement some of the accomplishments described in the book. Rather than organizing this book in a subject driven way, it is essentially organized according to the common economic regions of the world, as defined by the United Nations (Africa, Asia and the Pacific, Europe, Latin America and the Caribbean, Western Asia). This allows better recognition of the importance of a regional (and at times) global approach to basic space science for the developing nation's world wide. It highlights very specific scientific investigations which have been completed successfully in the various developing nations. The book supplements the published ten volumes of workshop proceedings containing scientific papers presented in the workshops from 1991 to 2002. Information on the workshops is also available at http://www seas.columbia.edu/~ah297/un-esa/index.html http://www oosa.unvienna.org/SAP/bss/index.html http://www oosa.unvienna.org/SAP/centres/centres.html

Modern astrophysics is a mature science that has evolved from its early phase of discovery and classification to a physics-oriented discipline focused on finding answers to fundamental problems ranging from cosmology to the origin and diversity of life-sustainable systems in the Universe. For this very reason, progress of modern astrophysics requires access to the electromagnetic spectrum in the broadest energy range. The Ultraviolet is a fundamental energy domain since it is one of the most powerful tools to study plasmas at temperatures in the 3,000-300,000~K range as well as electronic transitions of the most abundant molecules in the Universe. Moreover, the UV radiation field is a powerful astrochemical and photoionizing agent.This book describes the fundamental problems in modern astrophysics that cannot progress without easy and wide-spread access to modern UV instrumentation.

This book brings together the historical activities, the plans which have been developed over the past decade in the different nations, and the results which have materialized during this time in different developing nations. It aims to achieve for development agencies to be assisted in ways to find more effective tools for the application of development aid. The last section of the book contains a guide for teachers to introduce astrophysics into university physics courses. This will be of use to teachers in many nations.

Modern astrophysics is a mature science that has evolved from its early phase of discovery and classification to a physics-oriented discipline focused on finding answers to fundamental problems ranging from cosmology to the origin and diversity of life-sustainable systems in the Universe. For this very reason, progress of modern astrophysics requires access to the electromagnetic spectrum in the broadest energy range. The Ultraviolet is a fundamental energy domain since it is one of the most powerful tools to study plasmas at temperatures in the 3,000-300,000~K range as well as electronic transitions of the most abundant molecules in the Universe. Moreover, the UV radiation field is a powerful astrochemical and photoionizing agent.This book describes the fundamental problems in modern astrophysics that cannot progress without easy and wide-spread access to modern UV instrumentation.

ROSAT Observations G. HASINGER Max-Planck-Institut flir extraterrestrische Physik, D-85740 Garching, Germany Abstract. This review describes the most recent advances in the study of the extragalactic soft X-ray background and what we can learn about its constituents. The deepest pointed observations with the ROSAT PSPC are discussed. The logN-logS relation is presented, which reaches to the faintest X-ray fluxes and to the highest AGN surface densities ever achieved. The N(>S) relation shows a 2 density in excess of 400 deg- at the faintest fluxes and a flattening below the Einstein Deep Survey limit. About 60% of the extragalactic background has been resolved in the deepest field. Detailed source spectra and first optical and radio identifications will be discussed. The results are put into perspective of the higher energy X -ray background. Key words: X-rays, background radiations, active galactic nuclei. 1. Introduction The extragalactic X-ray background (XRB), discovered about 30 years ago, has been studied extensively with many X-ray experiments, in particular with the satel­ lites HEAO I and II (see ego Boldt 1987) and with ROSAT (e. g. Hasinger et aI. , 1993). Figure 1 shows a compilation of some of the most recent spectral measure­ ments for the X-ray background. Over the energy range from 3 to about 100 keY its spectrum can be well approximated by an optically thin thermal bremsstrahlung model with kT ~ 40 keY, while at lower X-ray energies a steepening into a new component has been observed observed (e. g.