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  • 1
    ISSN: 1432-0754
    Keywords: Interstellar dust ; grain mantles ; CO abundance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The presence of solid carbon monoxide (CO) on interstellar grains was confirmed observationally in 1984 with the detection of infrared absorption at 4.67μm wavelength in several molecular clouds. Subsequent observations suggest that solid CO is ubiquitous in the quiescent molecular cloud environment. In some lines of sight, the degree of frosting on to grains is sufficient to reduce appreciably the abundance of CO remaining in the gas, a result of considerable astrophysical significance: in addition to its importance as a tracer of molecular material, CO is vital to the production of many polyatomic molecules by gas phase reaction schemes, and its depletion could have a dramatic effect on the abundances of more complex carbon-bearing molecules. The infrared spectrum of solid CO provides an important diagnostic of the chemical composition and thermal evolution of grain mantles, leading to the prediction that CO2 is also present in solid form. As it is now some six years since observations of interstellar solid CO were first reported, this is an appropriate time to review the topic and to suggest some directions for future research. The introduction (Sect. 1) attempts to place the subject in its broader astrophysical context. The infrared observations and their implications are discussed in detail in Sect. 2. The question of the degree of CO depletion implied by the observations of both solid state and gas phase CO is re-examined in Sect. 3. We assess the possibility of CO detection by means of solid state absorption or luminescence in the ultraviolet in Sect. 4. Future prospects are summarised in the final section.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0754
    Keywords: Galaxy ; evolution-Stars ; abundances, mass loss-Interstellar medium ; dust, molecules-Solar System ; formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary This paper traces the evolution of the biogenic elements H, C, N, O, P and S from their creation by cosmic nucleosynthesis to their inclusion in living systems on the surface of the Earth. Evidence for the presence of significant prebiotic molecules in interstellar clouds and in primitive meteorites is reviewed. The possible relevance of this discovery to the origin of life on Earth is assessed in the light of evidence suggesting that such molecules could not easily be synthesized in a primitive CO2-dominated terrestrial atmosphere.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 305 (1983), S. 161-161 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] WHITTET REPLIES-The conclusion drawn by Hoyle and Wickramasinghe must be treated with caution, as it is based on the assumption that C-H bond absorption in organic polymers is the only possible explanation of the long-wavelength 'shoulder' in the 3.1-p? interstellar ice band profile. As pointed out ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] GK Persei underwent a classical nova outburst in 1901, reaching visual magnitude (V) of 0.2 on 22 February 1901. Subsequently, it declined at 0.23 mag per day, reaching a minimum typically of V = 13.1 (ref. 2). In contrast with other objects of this type, GK Per shows dwarf nova-like outbursts of ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 303 (1983), S. 218-221 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ice was first suggested1 as a constituent of interstellar grains in 1935 *; subsequently, a detailed grain model was developed2 based on the nucleation and growth of ice grains in interstellar clouds, a model which achieved widespread acceptance for many years3. However, IR astronomy has ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 281 (1979), S. 708-708 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IT has become fashionable to discuss the possibility that interstellar grains may contain significant quantities of organic material (see réf. 1 and refs therein). I draw attention here to new data which preclude the presence of most organic solids as a significant component of the grains in ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE IUE with its wide spectral coverage, roughly 1,150-3,200 Å embracing many of the resonance lines of the common elements, its excellent sensitivity throughout this band, and its large resolving power of 104 when used in the high dispersion mode, is a unique instrument for studying the ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 303 (1983), S. 218-221 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ice was first suggested1 as a constituent of interstellar grains in 1935 *; subsequently, a detailed grain model was developed2 based on the nucleation and growth of ice grains in interstellar clouds, a model which achieved widespread acceptance for many years3. However, IR astronomy has ...
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2013-08-31
    Description: Researchers spectrum of NGC 4565 is essentially featureless. The absence of the 3.0 micron feature (Tau 3.0 less than 0.05) implies that the extinction to the nucleus does not arise to a significant degree in molecular clouds. Researchers deduce Tau 3.0/A sub V less than 0.01, compared with approx. 0.022 for GC-IRS7. These results support the conclusion (McFadzean et al. 1989) that the 3.0 micron absorption in the GC-IR sources is due to the presence of ice in a (probably single) foreground molecular cloud. The 3.4 micron feature is also weak or absent in the researchers spectrum of NGC 4565 (Tau 3.4 less than or equal to 0.07), hence, Tau 3.4/A sub V less than or equal to 0.016, compared with approx. 0.008 towards GC-IRS7. The absence of the feature in NGC 4565 at the signal-to-noise level of the current observations is consistent with a probable moderate degree of extinction towards the nucleus. The observations of NGC 4565 provide a useful comparison for studies of dust in the Galaxy. Limits have been set on the strengths of the 3.0 and 3.4 micron features in NGC 4565. The absence of 3.0 micron absorption is significant, and supports the view that the feature at this wavelength in the Galactic Centre is due to water-ice absorption in a foreground molecular cloud. The non-detection of the 3.4 micron absorption is less surprising and provides indirect support for the association between this feature and the diffuse interstellar medium. The current spectrum probably represents the best that can be achieved with a single-detector instrument within reasonable integration times. It will clearly be of interest in the future to obtain spectra of higher signal-to-noise, as a positive detection of the 3.4 micron feature in an external galaxy, even at a low level, would be of considerable astrophysical significance.
    Keywords: ASTROPHYSICS
    Type: NASA, Ames Research Center, The Interstellar Medium in External Galaxies: Summaries of Contributed Papers; p 89-91
    Format: application/pdf
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  • 10
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract I review the relative importance of internal and external sources of prebiotic molecules on Earth at the time of life's origin μ3.7Gyr ago. The efficiency ofsynthesis in the Earth's atmosphere was critically dependent on its oxidation state. If the early atmosphere was non-reducing and CO2-dominated, external delivery might havebeen the dominant source. Interplanetary dust grains and micrometeorites currently deliver carbonaceous matter to the Earth's surface at a rate of μ 3 × 105kg/yr(equivalent to a biomass in μ2Gyr), but this may havebeen as high as 5 × 107kg/yr (a biomass in onlyμ10Myr) during the epoch of late bombardment. Much ofthe incoming material is in the form of chemically inactive kerogens and amorphous carbon; but if the Earth once had a dense (μ10-bar) atmosphere, small comets rich in avariety of prebiotic molecules may have been sufficiently air-braked to land non-destructively. Lingering uncertainties regarding the impact history of the Earth and the density and composition of its early atmosphere limit our ability to draw firm conclusions.
    Type of Medium: Electronic Resource
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