Evidence for interstellar SiC in the Murray carbonaceous meteorite

Bernatowicz, T. J.; Fraundorf, G. K.; Tang, Ming; Anders, Edward; Wopenka, B.; Zinner, E.; Fraundorf, P.

doi:10.1038/330728a0

Cited by 319 publications

(175 citation statements)

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“…Furthermore, presolar SiC grains have been found in meteorites and IDPs (see e.g. Bernatowicz et al 1987). SiC displays a strong spectral resonance around 11 µm.…”

Section: Effects Of Grain Compositionmentioning

confidence: 99%

The shape and composition of interstellar silicate grains

Min

Waters

Koter

et al. 2006

A&A

192

225

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We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effects of the amount of magnesium and iron in the silicate lattice are studied in detail. We fit the spectral shape of the interstellar 10 µm extinction feature as observed towards the galactic center using various particle shapes and dust materials. We use very irregularly shaped coated and non-coated porous Gaussian Random Field particles as well as a statistical approach to model shape effects. For the dust materials we use amorphous and crystalline silicates with various composition as well as silicon carbide (SiC). The results of our analysis of the 10 µm feature are used to compute the shape of the 20 µm silicate feature and to compare this with observations of this feature towards the galactic center. By using realistic particle shapes to fit the interstellar extinction spectrum we are, for the first time, able to derive the magnesium fraction in interstellar silicates. We find that the interstellar silicates are highly magnesium rich (Mg/(Fe + Mg) > 0.9) and that the stoichiometry lies between pyroxene and olivine type silicates (O/Si ≈ 3.5). This composition is not consistent with that of the glassy material found in GEMS in interplanetary dust particles indicating that the amorphous silicates found in the Solar system are, in general, not unprocessed remnants from the interstellar medium. Also, we find that a significant fraction of silicon carbide (∼3%) is present in the interstellar dust grains. We discuss the implications of our results for the formation and evolutionary history of cometary and circumstellar dust. We argue that the fact that crystalline silicates in cometary and circumstellar grains are almost purely magnesium silicates is a natural consequence of our findings that the amorphous silicates from which they were formed were already magnesium rich.

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“…Furthermore, presolar SiC grains have been found in meteorites and IDPs (see e.g. Bernatowicz et al 1987). SiC displays a strong spectral resonance around 11 µm.…”

Section: Effects Of Grain Compositionmentioning

confidence: 99%

The shape and composition of interstellar silicate grains

Min

Waters

Koter

et al. 2006

A&A

192

225

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“…The first mineral type of presolar grains, diamond, was identified and isolated in 1987 [1]. The mineral types of presolar grains identified to date include diamond [1], SiC [2,3], graphite [4], oxides [5][6][7], Si 3 N 4 [8], silicates [9][10][11][12], and refractory carbides inside graphite or SiC host grains [13]. Their abundances range from a few hundred ppm to down to a few ppb [14,15].…”

Section: Introductionmentioning

confidence: 99%

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

Amari¹

2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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Presolar SiC and graphite grains are the grain types whose isotopic signatures have been extensively studied. Isotopic compositions of light and intermediate elements in single grains have been analyzed mostly using secondary ion mass spectrometry. Detailed information about nucleosynthetic conditions can be obtained from isotopic compositions of heavy elements. Isotopic compositions of heavy elements in SiC and graphite grains have been analyzed using resonant ionization mass spectrometry. Analyses of heavy elements and noble gases are likely to produce new insights into presolar grains using newly-developed instruments.

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“…SiC is observed in circumstellar envelopes of carbon stars and planetary nebulae (e.g. Bode, 1988), and pre-solar SiC is detected in meteorites (Bernatowicz et al, 1987).…”

Section: Refractory Compositionmentioning

confidence: 99%

Chemical Composition of Dust Expected from Condensation Models

Yamamoto

1991

International Astronomical Union Colloquium

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ABSTRACT. This review examines to what degrees the present chemical equilibrium condensation models are effective in predicting chemical composition of grains observed in a variety of cosmic environments. The composition expected from the equilibrium calculations is reviewed separately for refractory (rocky and metallic) and volatile (icy) components. Comments are given on the limitation of the equilibrium calculations in predicting the grain composition. By taking cometary ice as a typical cosmic volatile condensate, it is pointed out that its composition is far from that expected from the equilibrium models. Theories on the formation of cometary volatiles are reviewed, and an observational clue helpful to testing the theories is pointed out. Discussion is given on the advantage for formation of organic materials from volatile solids.

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Evidence for interstellar SiC in the Murray carbonaceous meteorite

Cited by 319 publications

References 0 publications

The shape and composition of interstellar silicate grains

The shape and composition of interstellar silicate grains

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

Chemical Composition of Dust Expected from Condensation Models

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