Composition, structure and chemistry of interstellar dust

Technical Report · Mon Sep 01 04:00:00 EDT 1986

OSTI ID:5554510

Tielens, A G.G.M.; Allamandola, L J

The observational constraints on the composition of the interstellar dust are analyzed. The dust in the diffuse interstellar medium consists of a mixture of stardust (amorphous silicates, amorphous carbon, polycyclic aromatic hydrocarbons, and graphite) and interstellar medium dust (organic refractory material). Stardust seems to dominate in the local diffuse interstellar medium. Inside molecular clouds, however, icy grain mantles are also important. The structural differences between crystalline and amorphous materials, which lead to differences in the optical properties, are discussed. The astrophysical consequences are briefly examined. The physical principles of grain surface chemistry are discussed and applied to the formation of molecular hydrogen and icy grain mantles inside dense molecular clouds. Transformation of these icy grain mantles into the organic refractory dust component observed in the diffuse interstellar medium requires ultraviolet sources inside molecular clouds as well as radical diffusion promoted by transient heating of the mantle. The latter process also returns a considerable fraction of the molecules in the grain mantle to the gas phase.

• Research Organization: National Aeronautics and Space Administration, Moffett Field, CA (USA). Ames Research Center
• OSTI ID: 5554510
• Report Number(s): N-88-11603; NASA-TM-88350; A-86383; NAS-1.15:88350
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CARBON
CHEMICAL COMPOSITION
COSMIC DUST
CRYSTAL STRUCTURE
DUSTS
ELEMENTAL MINERALS
ELEMENTS
GRAPHITE
HYDROCARBONS
HYDROGEN
ICE
INTERSTELLAR GRAINS
MINERALS
NONMETALS
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PARTICLES
PHYSICAL PROPERTIES
SILICATES
SILICON COMPOUNDS