Results 351 to 360 of about 4,372,191 (364)
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Stellar chemical abundances with the GHRS
Physica Scripta, 1996The accurate quantitative analysis of high resolution ultraviolet spectra of ultra-sharp-lined early-type, chemically peculiar stars, obtained with the Goddard High Resolution spectrograph on the Hubble Space Telescope, has been made possible by the synergism between state-of-the-art astro-physics and state-of-the-art atomic spectroscopy. We illustrate
Glenn M. Wahlgren +6 more
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1988
The precise determination of chemical abundances in stars is the key to a number of important disciplines in modern astrophysics including stellar evolution and nucleosynthesis as well as the chemical and dynamical evolution of the Galaxy. The basic transport mechanisms in stellar atmospheres rule the observational aspects of stellar surfaces which are
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The precise determination of chemical abundances in stars is the key to a number of important disciplines in modern astrophysics including stellar evolution and nucleosynthesis as well as the chemical and dynamical evolution of the Galaxy. The basic transport mechanisms in stellar atmospheres rule the observational aspects of stellar surfaces which are
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Chemical Abundances in Meteorites
1988Some 4.6 billion years ago contraction and subsequent collapse of an interstellar cloud led to the formation of the solar system. The ratio of heavy elements to hydrogen, increasing continuously in interstellar material, due to the addition of freshly synthesized material from stars, was frozen in for the solar system at this point of time.
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1981
Photoelectric, filter photometry and spectrophotometry allow us to derive absolute abundances for a number of species in comets. Despite large differences in morphology, in gas-to-dust ratio, and in dynamical age, there appears to be remarkably little variation from comet to comet in the relative production rates of the species studied thus far.
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Photoelectric, filter photometry and spectrophotometry allow us to derive absolute abundances for a number of species in comets. Despite large differences in morphology, in gas-to-dust ratio, and in dynamical age, there appears to be remarkably little variation from comet to comet in the relative production rates of the species studied thus far.
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Chemical Abundances in Galaxies
1988This article is intended as a brief overview of chemical abundances in galaxies other than our own. Attention is concentrated on global properties of ellipticals and spirals, and the methods by which abundances are estimated. References are predominantly to work which has appeared since the review of Pagel and Edmunds (1981).
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Chemical Abundances in Molecular Clouds
1987At present approximately 70 interstellar molecules are known. We discuss methods for determining chemical abundances in interstellar clouds and present results for the best studied regions, which include the “spiral arm” clouds seen towards distant continuum sources, quiescent dark and giant clouds, and the gas in regions of active star formation.
Paul F. Goldsmith +2 more
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Chemical Abundances and Galaxy Evolution [PDF]
, 1984 The chemical abundance characteristics of two comparatively structurally simple classes of galaxies, the ellipticals and irregulars, are briefly reviewed. Neither of these types of galaxies have properties which are fully consistent with the quantitative predictions of basic chemical evolution models. Possible sources for discrepancies are discussed in
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Chemical Abundances in Old Populations
1992Preliminary single-burst population synthesis models are presented for weak and strong spectral features as a function of metallicity for old populations. Models agree with published globular cluster observations as well as theoretical calibrations. For small ellipticals, the galaxies and model predictions agree well in all indices.
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