Isotopic Ratios in Comets
نویسندگان
چکیده
منابع مشابه
Isotopic abundance of nitrogen and carbon in distant comets
The CN/CN and CN/CN isotopic ratios have been determined in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT) and C/2003 K4 (LINEAR) at heliocentric distances of, respectively, 2.7, 3.7 and 2.6 AU. These ratios have also been measured at r ∼ 1 AU. No significant differences were found between all determinations, nor with the value obtained for other comets. If confirmed, the discrepancy between th...
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From high resolution spectra of 61 cool dwarfs and giants, Mg isotopic abundance ratios Mg:Mg:Mg are derived from spectral synthesis of the MgH A-X lines near 5140Å. Our sample spans the range −2.5 ≤ [Fe/H] ≤ 0.1, including the first measurements of Mg isotope ratios in stars with metallicities below [Fe/H]=−2.0. We confirm the decrease in Mg/Mg with decreasing [Fe/H] as predicted by recent mod...
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Although mainstream SiC grains, the major group of presolar SiC grains found in meteorites, are believed to have originated in the expanding envelope of asymptotic giant branch (AGB) stars during their late carbon-rich phases, their Si isotopic ratios show a distribution that cannot be explained by nucleosynthesis in this kind of stars. Previously, this distribution has been interpreted to be t...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1991
ISSN: 0252-9211
DOI: 10.1017/s0252921100012756