Dust is a ubiquitous feature of the cosmos, impinging directly or indirectly on most fields of modern astronomy and astrophysics. Dust in the Galactic Environment, Second Edition provides a thorough overview of the subject, covering general concepts, methods of investigation, important results and their significance, relevant literature, and some suggestions for promising avenues of future research. Since the publication of the first edition of this popular graduate text, major advances have been made in our understanding of astrophysical dust, especially in the light of exciting new results from space- and ground-based telescopes, together with advances in laboratory astrophysics and theoretical modeling. This new, expanded edition highlights the latest results and provides a context for future research opportunities. The first chapter provides a historical perspective for current research and an overview of interstellar environments and the role of dust in astrophysical processes, followed by a discussion of the cosmic history of the chemical elements expected to be present in dust and an examination of the effect of gas-dust interactions on gas phase abundances. The next several chapters describe the observed properties of interstellar grains, such as their extinction, polarization, absorption, and emission characteristics. Then, the book explores the origin and evolution of dust, tracing its life cycle in a succession of environments from circumstellar shells to diffuse interstellar clouds, molecular clouds, protostars, and protoplanetary disks. The final chapter summarizes progress toward a unified model. Dust in other galaxies is discussed as an integral part of the text rather than as a distinct topic requiring separate chapters. Containing extensive references and problems to aid understanding and illustrate basic principles, the book is ideally suited for graduate and advanced undergraduate courses. It will also be an invaluable reference for postgraduate students and researchers working in this important field.

Dust in the Galactic Environment, Third Edition provides a thorough overview of the subject, covering general concepts, methods of investigation, important results and their significance, relevant literature, and some suggestions for promising avenues of future research. Major advances have been made in the last two decades in our understanding of astrophysical dust. These have been driven by discoveries arising from new observational facilities such as the Spitzer, Planck, and Herschel Space Telescopes, as well as important parallel developments in laboratory studies of cosmic and terrestrial analog materials. This new, expanded edition reviews these developments, summarizes the current state of the field, and considers possibilities for future advances, for example with the James Webb Space Telescope. It includes introductory material for new entrants to the field alongside detailed discussion for more advanced students and researchers.

The mysterious "21 micron" emission feature seen almost exclusively in the short-lived protoplanetary nebula (PPN) phase of stellar evolution remains unidentified since its discovery two decades ago. This feature is always accompanied by the equally mysterious, unidentified "30 micron" feature and the so-called "unidentified infrared" (UIR) features at 3.3, 6.2, 7.7, 8.6, and 11.3 micron which are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. We explore the interrelations among the mysterious 21 micron, 30 micron, and UIR features of the 21 micron sources. We find that none of these spectral features correlate with each other. This argues against a common carrier (e.g., thiourea) for both the 21 micron feature and the 30 micron feature. This also does not support large PAH clusters as a possible carrier for the 21 micron feature. We also derive the stellar mass loss rates of these 21 micron sources from their dust infrared (IR) emission, using the "2-DUST" radiative transfer code for axisymmetric dusty systems and examine the correlation between mass loss rate of AGB phase or mass loss rate of superwind phase with that of fluxes emitted from 21 and 30 micron features. In addition, we probe the role of carbon in the ultraviolet (UV) extinction by examining the relations between the amount of carbon required to be locked up in dust with the 2175 Angstrom extinction bump and the far-UV extinction rise, based on an analysis of the extinction curves along 16 Galactic sightlines. We derive abundances of carbon from the model-independent Kramers-Kronig relation which relates the wavelength-integrated extinction to the total dust volume and is less model-dependent. We also derive carbon abundance from fitting the observed UV/optical/near infrared extinction with a mixture of amorphous silicate and graphite. We find that the carbon depletion tends to correlate with the strength of the 2175 Angstrom bump, while the abundance of silicon depleted in dust shows no correlation with the 2175 Angstrom bump. This supports graphite or polycyclic aromatic hydrocarbon (PAH) molecules as the possible carrier of the 2175 Angstrom bump. We also see that carbon abundance shows a trend of correlating with 1/R(V) where R(V) is the total-to-selective extinction ratio, suggesting that the far-UV extinction is more likely produced by small carbon dust than by small silicate dust. Finally, we model the infrared emission of 120 Galactic high latitude clouds and 81 Diffuse Infrared (DIR) excess clouds using silicate-graphite-PAH model. They exhibit notable cloud-to-cloud variations in the midinfrared, with the ratio of the IRAS 12 micron intensity to the IRAS 25 micron intensity varying by up to one order of magnitude. We find that hydrogen column density strongly correlates with the far-infrared emission, this indicates the presence of large grains of similar properties and abundances. Also, we find that all clouds are rich in PAHs as traced by the IRAS 12 micron data. They are heated by the local interstellar radiation field, but with the radiation intensity reduced by a factor of about 2 to 3.

- First book to present a comprehensive study of dust in the universe

Written by experts who created the field, this volume explores uncharted scientific territory, with articles discussing the effect of our galactic environment on the heliosphere, planetary system and Earth. Leading experts in diverse fields discuss the physical changes expected as the heliosphere adjusts to its galactic environment. Topics include the interaction between solar wind and interstellar dust and gas, cosmic ray modulation, magnetospheres, variations in the solar environment, and the cosmic ray isotope record preserved in paleoclimate data.