Thoroughly revised and expanded throughout, the new edition is a graduate-level text and reference book on gaseous nebulae, nova and supernova remnants. Much of the new data and new images are from the Hubble Space Telescope with two wholly new chapters being added along with other new features. The previous edition which was tried and tested for thirty years has now been succeeded by a revised, updated, larger edition, which will be valuable to anyone seriously interested in astrophysics.

This book provides a comprehensive survey of modern molecular astrophysics. It includes an introduction to molecular spectroscopy and then addresses the main areas of current molecular astrophysics, including galaxy formation, star forming regions, mass loss from young as well as highlyevolved stars and supernovae, starburst galaxies plus the tori and discs near the central engines of active galactic nuclei. All chapters have been written by invited authors who are acknowledged experts in their fields. The thorough editorial process has ensured a uniformly high standard ofexposition and a coherent style. The book is unique in giving a detailed view of its wide-ranging subject. It will provide the standard introduction for research students in molecular astrophysics. The book will be read by research astronomers and astrophysicists who wish to broaden the basis oftheir knowledge or are moving their activities into this burgeoning field. It will enable chemists to learn the astrophysics most related to chemistry as well as instruct physicists about the molecular processes most important in astronomy.

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This volume is the documentation of the first Course on 'Neutron Stars, Active Galactic Nuclei and Jets', of an Erice School with a wide astro physical scope. The choice of the subject was made because of an apparent similari ty - stressed already at earlier meetings - of four classes of astrophy sical jet sources: Active Galactic Nuclei, Young Stellar Objects, Binary Neutron Stars and Binary White Dwarfs. They share important properties such as their morphology, high variability and large veloci ty gradients as well as - with some inference - their broad spectrum, hypersonic outflow and core/lobe power ratio. Despite this apparent similarity of the four source classes, quite different models have been put forward for their description: (i) The central engine of active galactic nuclei has been generally thought to be a black hole, in contrast to the central engine of young stellar objects and cometary nebulae which apparently is a pre-T-Tauri star, some six orders of magnitude less compact, and to the central engine of planetary nebulae which mayor may not be a binary white dwarf. (ii) The elongated lobes, or flow patterns, have been often interpreted as highly directional stellar wind outflows whereas in a few well mapped cases, the elongated flow appears to be 'pumped up' through a much narrower channel, or jet, both in the extragalactic and stellar sources.

Almost all galaxies host in their center a supermassive black hole of mass between a million and tens of billions solar masses. Supermassive black holes grow in symbiosis with their host galaxies across the Hubble time, occasionally accreting surround matter, giving rise to an Active Galactic Nuclei (AGN). This book gives a general review of our current knowledge of AGN, powered by supermassive black holes: how they are fueled by gas (or stars) and what problems are encountered; how can we account for the wide variety of AGN, from Seyfert/Liners to quasars, and for the two types (AGN 1 and 2) either through dust obscuration, and geometrical orientation arguments, or through intrinsic activity difference, qualitative or quantitative.

A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.