Graphite Grains and Graphite-Core-Ice-Mantle Grains
نویسندگان
چکیده
منابع مشابه
Extinction by porous silicate and graphite grains
Discrete dipole approximation (DDA) is used to calculate extinction efficiencies of porous silicate and graphite grains. We apply DDA first to the spheroidal solid grains assumed to be made of a large number of small scattering elements (dipoles). Then we systematically reduce the number of dipoles to model the porous grains. The extinction is studied as a function of wavelength, grain size and...
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Presolar grains are sub-micron to micron-sized stardust grains that are found in very primitive solar system materials. Laboratory measurements of presolar grains allow cosmochemists to understand the chemical and physical conditions in circumstellar environments, where the grains condensed. They provide important constraints for models of stellar nucleosynthesis and Galactic chemical evolution...
متن کاملIsotopic analysis of presolar graphite grains from Orgueil
We report the successful isolation and isotopic analysis of presolar graphite grains from the Orgueil CI chondrite. Isotopic measurements were made on seven density fractions, with grain sizes >1 lm: ORG1b (1.59–1.67 g cm ), 1c (1.67–1.75 g cm ), 1d (1.75– 1.92 g cm ), 1f (2.02–2.04 g cm ), 1g (2.04–2.12 g cm ), 1h (2.12–2.16 g cm ) and 1i (2.16–2.30 g cm ). We measured C, N, O, and Si isotopes...
متن کاملNew Stellar Sources for High-density, Presolar Graphite Grains
We present C, N, O, Si, Al-Mg, K, Ca, and Ti isotopic analyses of seven high-density (ORG1f, 2:02 2:04 g cm ) graphite grains from Orgueil with C/C ratios smaller than 20. The presence of 44Ti in three of these grains indicates an origin in Type II supernovae (SNe). The C excesses in these SNe grains, however, remain enigmatic. The remaining grains have extremely large Ca and Ti isotopic anomal...
متن کاملContinued Isotopic Studies of Low-density Graphite Grains from Orgueil
Jadhav, S. Amari, E. Zinner and T. Maruoka*, Laboratory for Space Sciences and the Department of Earth and Planetary Sciences ([email protected]), Laboratory for Space Sciences and the Physics Department, Washington University in St. Louis, One Brookings Dr., St. Louis, MO 63130, USA., * present address: Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1965
ISSN: 0252-9211
DOI: 10.1017/s0252921100118445