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Aims. We studied the evolution of the abundance in interstellar dust species that originate in stellar sources and from condensation in molecular clouds in the local interstellar medium of the Milky Way. We determined from this the input of dust material to the Solar System. Methods. A one-zone chemical evolution model of the Milky Way for the elemental composition of the disk combined with an evolution model for its interstellar dust component similar to that of Dwek (1998) is developed. The dust model considers dust-mass return from AGB stars as calculated from synthetic AGB models combined with models for dust condensation in stellar outflows. Supernova dust formation is included in a simple parametrised form that is gauged by observed abundances of presolar dust grains with a supernova origin. For dust growth in the ISM, a simple method is developed for coupling this with disk and dust evolution models. Results. A chemical evolution model of the solar neighbourhood in the Milky Way is calculated, which forms the basis for calculating a model of the evolution of the interstellar dust population at the galactocentric radius of the Milky Way. The model successfully passes all standard tests for the reliability of such models. In particular the abundance evolution of the important dust-forming elements is compared with observational results for the metallicity-dependent evolution of the abundances for G-type stars from the solar neighbourhood. It is found that the new tables of Nomoto et al. (2006) for the heavy element production give much better results for the abundance evolution of these important elements than the widely used tables of . The time evolution for the abundance of the following dust species is followed in the model: silicate, carbon, silicon carbide, and iron dust from AGB stars and from supernovae, as well as silicate, carbon, and iron dust grown in molecular clouds. It is shown that the interstellar dust population is dominated by dust accreted in molecular clouds; stardust only forms a minor fraction. Most of the dust material entering the Solar System at its formation does not show isotopic abundance anomalies of the refractory elements, i.e., inconspicuous isotopic abundances do not point to a Solar System origin for dust grains. The observed abundance ratios of presolar dust grains formed in supernova ejecta and in AGB star outflows requires that, for the ejecta from supernovae, the fraction of refractory elements condensed into dust is 0.15 for carbon dust and is quite small (∼10 −4 ) for other dust species.

The composition of the dust mixture and the amounts of dust returned into the interstellar medium during the evolution of low and intermediate mass stars on the AGB is calculated by simple models for dust-forming stellar winds with M-, S-, and C-star chemistry. These models consider the most abundant dust species formed in circumstellar dust shells, i.e. olivine-and pyroxene-type silicate grains and iron grains in the case of M-stars, iron grains in the case of S-stars, and carbon, SiC, and iron grains in the case of C-stars. The wind models are combined with calculations of synthetic AGB-evolution to consistently determine the variation of the dust injection rate into the interstellar medium from AGB-stars with initial mass and metallicity as the stars evolve along the AGB and change their chemical surface compositions due to repeated "dredge-up" episodes. Numerical results are presented for initial stellar masses from 1 to 7 M and for metallicities between Z = 0.001 and Z = 0.04, which can then be used to calculate chemical evolution models for the dust content of galaxies.

Circumstellar dust, the astronomical dust that forms around a star, provides today's researchers with important clues for understanding how the Universe has evolved. This volume examines the structure, dynamics and observable consequences of the dust clouds surrounding highly evolved stars on the Giant Branch. Early chapters cover the physical and chemical basis of the formation of dust shells, the outflow of matter, and condensation processes, while offering detailed descriptions of techniques for calculating dust formation and growth. Later chapters showcase a wide range of modeling strategies, including chemical and radiative transfer and dust-induced non-linear dynamics, as well as the latest data obtained from AGB stars and other giants. This volume introduces graduate students and researchers to the theoretical description for modeling the dusty outflows from cool stars and provides a full understanding of the processes involved.

Abstract. The outer regions of protoplanetary accretion discs are formed by material from the parent molecular cloud of the freshly forming stars. The interstellar dust in this material is a mixture of species which does not correspond to any kind of chemical equilibrium state between the solid and gaseous phases. Mass accretion carries this material into the warm inner disc zones where chemical and physical processes are activated which convert the non-equilibrium solid-gas mixture into a chemical equilibrium mixture. Part of the equilibrated material is then mixed outwards by turbulent diffusion and large-scale circulation currents. This work specifically considers the evolution of the main dust components, viz. from the interstellar mixture of amorphous Mg-Fe-silicates, into a chemical equilibrium mixture of crystalline Mg-silicates, and iron. The basic set of equations for calculating the evolution of a mixture of silicates and iron is derived. Model calculations based on stationary, one-zone α-discs are combined with the advection-diffusion-reaction equations for the dust evolution to study the interstellar to equilibrium dust conversion and the radial mixing of equilibrated dust into the outer disc regions. This determines the mixture of the main dust components which form the mineral inventory of planetesimals. It is found that the results of the model calculation for the resulting mineral mixture are in rough agreement with the composition of matrix material of primitive meteorites and dust in cometary nuclei.

Abstract.The interplay between radial mixing process in protoplanetary accretion discs with processes leading to destruction or modification of the extinction properties of abundant dust species has significant consequences for the properties of the disk. This paper studies the consequences of annealing amorphous silicate dust at T ≈ 800 K, of combustion of the carbon dust component at about T ≈ 1000 K and of mixing the products into cold outer disc regions out to 10 AU and beyond. A model calculation in the one-zone approximation for stationary Keplerian α-disks around a solar-like protostar is combined with a solution of the equations for annealing of silicate dust grains, for carbon dust oxidation, and a solution of the diffusion equations for radial mixing of the dust components in the disc by turbulent flows. It is shown that annealing of amorphous silicate dust reduces the mass extinction coefficient of the disc matter by more than an order of magnitude in the warm disc zone. Radial mixing of the freshly produced crystalline silicate dust into outer disc regions reduces the opacity of the disc material also in cold disc regions where annealing is not possible. Mixing of carbon dust free material from the zone of carbon combustion into outer disc regions also leads to a considerable reduction of the opacity of the disc material. Radial mixing processes then modify the dust composition of the outer disc regions and by means of the dependence of the disk properties (midplane temperature Tc, viscosity ν, . . . ) on the opacity also modify the structure and evolution of a protoplanetary disc. It is shown that turbulent mixing processes in the protoplanetary accretion disc of a Solar System like system during its evolution prior to the onset of the formation of planetary bodies carry material from inner disc regions r < 1 AU outwards to at least 10. . . 20 AU. This offers a simple explanation of the findings that a significant fraction of the cometary silicate dust grains are crystallised and that the matrix material of primitive meteorites contains thermally processed crystalline dust material.

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