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  • ASTROPHYSICS  (97)
  • INSTRUMENTATION AND PHOTOGRAPHY  (45)
  • 1980-1984
  • 1975-1979  (142)
  • 1977  (142)
  • 1
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    Spectrum of the Kleinmann-Low nebula from 29 to 125 micrometers (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The infrared spectrum of the Kleinmann-Low nebula in M42 has been measured from 80 to 350 kaysers (approximately 29 to 125 microns) with a Michelson interferometer aboard the NASA Kuiper Airborne Observatory. The frequency spectrum peaks at about 185 kaysers. A simple model of the emission implies that the temperature is in the range 70-95 K and that the optical depth is at least 0.2 at the peak frequency. A possible absorption is seen at about 176 kaysers. Thermal emission by dust at a temperature of 71 K, with the absorption cross section proportional to frequency, provides a good fit to the data. Other thermal-emission models can also fit the spectrum. The data are compared with previous broad-band measurements. Upper limits are placed on expected line emission from the surrounding H II region at the position of the nebula.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 212
    Format: text
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  • 2
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    The micrometeoroid complex and evolution of the lunar regolith (1977)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: Monte Carlo-based computer calculations, as well as analytical approaches utilizing probabilistic arguments, were applied to gain insight into the principal regolith impact processes and their resulting kinetics. Craters 10 to 1500 m in diameter are largely responsible for the overall growth of the regolith. As a consequence the regolith has to be envisioned as a complex sequence of discrete ejecta blankets. Such blankets constitute first-order discontinuities in the evolving debris layer. The micrometeoroid complex then operates intensely on these fresh ejecta blankets and accomplishes only in an uppermost layer of approximately 1-mm thickness. The absolute flux of micrometeoroids based on lunar rock analyses averaged over the past few 10 to the 6th power years is approximately an order of magnitude lower than presentday satellite fluxes; however, there is indication that the flux increased in the past 10 to the 4th power years to become compatible with the satellite data. Furthermore, there is detailed evidence that the micrometeoroid complex existed throughout geologic time.
    Schlagwort(e): ASTROPHYSICS
    Materialart: The Soviet-Am. Conf. on Cosmochem. of the Moon and Planets, Pt. 2; p 605-635
    Format: application/pdf
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  • 3
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    Recent developments in parallel-grid, gas-scintillation proportional counters (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The problems of developing large-area, gas-scintillation proportional counters with high resolution are considered. It is found that simple large-area, parallel-grid proportional counters suffer from a variation in gain over the counter window. Some success has been achieved in overcoming this problem by focusing the charge cloud as it drifts into the multiplication region. Measurements are reported for various mixtures of argon and xenon as well as pure xenon.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
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  • 4
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    Velocity dispersions in galaxies. VI - Comparison of the nucleus and bulge of M31 (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 212
    Format: text
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  • 5
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    Gamma rays and large scale galactic structure (1977)
    In:  CASI
    Details
    Publikationsdatum: 2006-08-09
    Beschreibung: Gamma ray astronomy is now beginning to provide a new look at the galactic structure and the distribution of cosmic rays, both electrons and nucleons, within the galaxy. The observations are consistent with a galactic spiral-arm model in which the cosmic rays are linearly coupled to the interstellar gas on the scale of the spiral arms. The agreement between the predictions of the model and the observations for regions of the plane where both 21-cm and 2.6-mm CO surveys exist emphasizes the need to extend these observations to include the entire plane. Future gamma-ray observations with more sensitivity and better angular resolutions, combined with these radio surveys, should shed new light on the distribution of cosmic rays, the nature of the galaxy, and the location and intensity of the spiral arms.
    Schlagwort(e): ASTROPHYSICS
    Materialart: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 301-314
    Format: text
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  • 6
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    The relationship between the galactic matter distribution, cosmic-ray dynamics, and gamma-ray production (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The concept that cosmic-ray density is related to the matter to which cosmic rays are dynamically coupled through magnetic fields on the scale of galactic arm segments is considered with specific reference to gamma-ray astronomy. A model of the galactic-matter and cosmic-ray distributions is developed on the basis of 21-cm radio surveys and recent observations of the 2.6-mm CO emission line by assuming that cosmic rays are galactic in origin, their column density is proportional to the total interstellar-gas column density, their scale height is considerably larger than that of the matter, and the Galaxy is a spiral with an arm/interarm density ratio of about 3 to 1. It is found that there is a good correlation between the observed gamma-ray intensity and that predicted on the basis of essentially complete coupling of cosmic rays to the best estimate of atomic and molecular hydrogen in the Galaxy. Individual maxima observed in gamma-radiation from the central region of the Galaxy are shown to be well correlated with those predicted to result from certain spiral-arm tangents if all the matter is assumed to be modulated in a particular spiral-arm segment pattern.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 215
    Format: text
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  • 7
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    Spectral radiance calibrations between 165-300 nm - An interlaboratory comparison (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The spectral radiance of deuterium lamps calibrated by the Max-Planck-Institut fuer Astronomie (MPI), by the U.S. National Bureau of Standards (NBS), and by the Physikalisch-Technische Bundesanstalt (PTB) are compared to check the agreement of UV radiometric scales. The NBS group used the optically thin continuum radiation from a wall-stabilized hydrogen arc as its fundamental radiometric standard, while the MPI and PTB groups used the synchrotron radiation facility in DESY. It is found that the spectral radiance scales based upon the DESY synchrotron and the NBS hydrogen arc are consistent, at least for one wavelength relative to another.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 16; July 197
    Format: text
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  • 8
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    Early history of the moon: Implications of U-Th-Pb and Rb-Sr systematics (1977)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: Anorthosite 60015 contains the lowest initial Sr-87/Sr-86 ratio yet reported for a lunar sample. The initial ratio is equal to that of the achondrite Angra dos Reis and slightly higher than the lowest measured Sr-87/Sr-86 ratio for an inclusion in the C3 carbonaceous chondrite Allende. The Pb-Pb ages of both Angra does Reis and Allende are 4.62 X 10 to the ninth power yr. Thus, the initial Sr/87/Sr-86 ratio found in lunar anorthosite 60015 strongly supports the hypothesis that the age of the Moon is about 4.65 b.y. The U-238/Pb-204 value estimated for the source of the excess lead in "orange soil" 74220 is approximately 35 and lower than the values estimated for the sources of KREEP (600-1000), high-K (300-600), and low-K (100-300) basalts. From these and other physical, chemical and petrographic results it was hypothesized that (1) the moon formed approximately 4.65 b.y. ago; (2) a global-scale gravitational differentiation occurred at the beginning of lunar history; and (3) the differentiation resulted in a radical chemical and mineralogical zoning in which the U-238/Pb-204 ratios increased toward the surface, with the exception of the low U-238/Pb-204 surficial anorthositic layer which "floated" at the beginning of the differentiation relative to the denser pyroxene-rich material.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA, Washington The Soviet-Am. Conf. on Cosmochem. of the Moon and Planets, Pt. 2; p 507-523
    Format: application/pdf
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  • 9
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    The decompression of cold neutron star matter (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The ejection of cold neutron-star matter is examined, and an attempt is made to determine whether the final composition of this matter may be similar to that normally associated with the hot high-neutron-flux r-process. A semiempirical liquid-drop model is used for the nucleus, and the equilibrium composition of the matter is determined by assuming it to be in its absolute ground state at a given density. Physical mechanisms operating during the expansion are analyzed, and the composition of the ejected matter is found as a function of its density during expansion. The results indicate that it is virtually impossible for deuterium to form, that neutrons can be captured only after beta decay increases the atomic numbers of nuclei, and that no free neutrons can escape. It is concluded that neutron-star ejecta can produce heavy neutron-rich nuclei and may produce somewhat heavier nuclei than a standard r-process.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 213
    Format: text
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  • 10
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    The compact radio sources in 4C 39.25 and 3C 345 (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Long-baseline interferometry of the quasars 4C 39.25 and 3C 345 at 10.65 and 14.77 GHz shows that the centimeter radio source in each object is double, with component separations of 0.0020 arcsec (4C 39.25) and 0.0013 arcsec (3C 345 at 1974.5). For each source, the separation is the same at both frequencies, as well as similar to the structure observed at 7.85 GHz (and 5.0 GHz for 4C 39.25). The spectra of the individual components are derived and shown to vary with time approximately as expected for expanding self-absorbed synchrotron sources. The magnetic fields in the components are estimated to be as high as 0.1 gauss, but the structure of the sources appears to be unrelated to the magnetic-field orientation derived from low-resolution polarization measurements. The component separation in 4C 39.25 has not changed for several years, whereas 3C 345 shows rapid expansion.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 218
    Format: text
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