Dust in the Universe

The following sections are included:

• Preface

• Contents

Study of the dust particles in the universe is an exciting and challenging area of current astronomy. This comes from various considerations. Dust is at the centre of all important events in the universe, like star formation, distance determination etc. Dust particles influence the thermal, dynamical, ionization and chemical states of matter of the interestellar and intergalactic medium. It may be noted, about half of the elements heavier than helium is in the form of dust in the interstellar medium of our Galaxy. Dust grains are effective absorbers of radiation energy and momentum. The collisional coupling between grains and gas in dense regions around evolved stars, in molecular cloud cores and protoplanetary disks have consequences for the temperature and the dynamical evolution of the gas component. The mass loss from evolved stars, stability of molecular clouds and their fragmentation into smaller clumps etc. are directly linked to the presence of dust. Infrared observations arising due to thermal emission from dust particles probe regions of star formation. The low temperature inside clouds arising from shielding of radiation by the dust particles leads to complex chemistry between dust and atoms and molecules. The formation of molecular hydrogen takes place on the surface of grains. The dust and complex chemistry of the material present in comets appear to be the same as in these clouds. May be these are the precursors to life on earth! However due to historical reasons and also due to lack of facilities both with regard to bigger telescopes and technology, most of the studies had to be concentrated on the local universe, particularly our Galaxy and nearby ones. Even here, until recently, studies were concentrated on brighter objects. Things have improved enormously with the advent of space and new technology telescopes. It is now possible to push the limit of observations to fainter and fainter sources. Also it has been possible to study objects farther in space and hence well back in time…

The following sections are included:

• Introduction

• Infrared Spectroscopy

• Mixed Ices

• Silicate
  • Structure of Silicate
  • Silicate Studies
    • Condensation
    • Effect of Environment
    • Silicon Nano-crystals
    • Optical Constants

• Carbon
  • Forms of Carbon
  • Carbon Studies

• Polycyclic Aromatic Hydrocarbons (PAHs)
  • Spectra
  • Mass Spectra
  • Steller Environment
  • Diffuse Interstellar Bands

• Optical Properties of Materials
  • Theoretical Considerations
  • Laboratory Measurements
  • Mass Absorption Coefficient
  • Microwave Scattering

• Microgravity Studies

• Nucleation

• Coagulation and Aggregation

• Other Dust Studies

• References

The following sections are included:

• Introduction

• Estimate of Amount of Extinction

• Effect on Derived Distances

• Amount of Absorbing Material

• Nature of Dust
  • Mean Interstellar Reddening Curve
  • Theoretical Extinction Curve
  • Variations in the Interstellar Extinction Curve

• Interstellar Polarization

• Scattered Light
  • Diffuse Galactic Light
  • Reflection Nebulae
  • The Extended Red Emission

• Elemental Depletion

• Diffuse Interstellar Bands

• Infrared Spectral Features
  • Diffuse Interstellar Medium
  • HII Region
  • Reflection Nebulae
  • Molecular Clouds
  • Processes in Molecular Clouds
  • Young Massive Protostar
  • Star-Forming Regions

• Galactic Centre
  • Extinction Law

• Sources of Dust

• Detection of Interstellar Dust:in-situ
  • Spacecraft Studies
  • Presolar Grains

• References

The following sections are included:

• Introduction

• Dust Tails
  • Dynamics of Dust Tails
  • Dust Trail

• Radiation Pressure Effects

• Visible Continuum

• Phase Function

• Polarization

• Infrared Observations

• Albedo

• Spectral Features in the Infrared
  • Spectral Features
  • Sizes of Grains

• Organics

• Water-Ice

• Mineralogical Composition

• Isotopic Studies

• References

The following sections are included:

• Introduction

• Interplanetary Dust Particles
  • Morphology, Structure and Chemical Composition
  • Origin

• Meteorites
  • Morphology, Structure and Chemical Composition
  • Presolar Grains
  • Time of Formation

• Extraterrestrial Origin
  • Presolar Grains

• References

The following sections are included:

• Introduction

• AGB Stars

• Mass Loss from Stars

• Theoretical Considerations
  • Dust Formation
  • Condensation of Dust
    • C/O < 1 (Oxygen-rich stars)
    • C/O > 1 (Carbon-rich stars)
    • C/O = 1 (S-Stars)
  • Circumstellar Chemistry

• Observational Results
  • Carbon-rich Stars
  • Oxygen-rich Stars
  • S Stars
  • UIR Bands in Oxygen-rich Supergiants
  • Stars of Other Type
    • Herbig Ae/Be Stars
    • Vega-Type Stars
  • Planetary Nebulae
  • Novae
  • Supernovae

• References

The following sections are included:

• Introduction

• Magellanic Cloud
  • Extinction Curve
  • Spectral Features

• Normal Galaxies

• Seyfert Galaxies

• Starburst Galaxies

• Ultraluminous Infrared Galaxies

• Merging Galaxies

• Virgo and Coma Clusters

• Quasars
  • Far-Infrared Radiation
  • Spectral Studies
    • Quasar Environment
    • Lyman α Forest
    • Damped Lyman α Systems

• Intergalactic Dust

• Intracluster Medium

• Cosmic Background Radiation
  • Cosmic Infrared Background Radiation
  • Cosmic Microwave Background Radiation

• References

Nature and composition of dust in the Universe is derived from astronomical observations and theoretical studies suplemented by laboratory studies of dust analogues. These aspects have been discussed in previous chapters. Nature of dust have been derived by various techniques. Some of the salient and important results resulting from these studies may be summarised as follows…

The following sections are included:

• Appendix A: H-R Diagram

• Appendix B: Stellar Evolution

• Appendix C: Nucleosynthesis

• Appendix D: Acronyms

• Index