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  • ASTROPHYSICS  (1,652)
  • LUNAR AND PLANETARY EXPLORATION  (1,415)
  • 1985-1989  (3,067)
  • 1980-1984
  • 1965-1969
  • 1950-1954
  • 1987  (1,643)
  • 1985  (1,424)
Collection
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  • 1985-1989  (3,067)
  • 1980-1984
  • 1965-1969
  • 1950-1954
Year
  • 1
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    Planetary atmospheres (1987)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Present understanding of planetary atmospheres is surveyed. The formation of the planets and their atmospheres is briefly reviewed, and attention is given to the compositions of the atmospheres of earth, Venus, and Mars, the outer planets, and Titan. Lists of the individual atmospheric gases and their concentrations are included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 2
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    Vehicle design for Mars surface exploration (1987)
    In:  CASI
    Details
    Publication Date: 2004-12-04
    Description: This design course is directed to studying problems related to mobile exploration of the surface of Mars. Constraints on the vehicles considered are set by the payload and performance currently envisioned by mission analysis carried out previously at the Jet Propulsion Laboratory. The students are given full flexibility to examine those aspects which suit their interests and background. There are no regularly scheduled class lectures. Weekly review meetings are held with personnel from the Jet Propulsion Laboratory, and students use JPL resources as required.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: USRA, Agenda of the Third Annual Summer Conference, NASA(USRA University Advanced Design Program; p 11
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  • 3
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    High-resolution lunar radar map at 70-cm wavelength (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: New radar observations of the moon in 1981-1984 were made using the 430 MHz (70 cm wavelength) radar at the Arecibo observatory, Puerto Rico. The new observations have produced a high resolution lunar radar map with radar cell-sizes near 2-5 km. This new resolution is a three-fold improvement over the previous mapping done in the late 1960's. Since the Arecibo radar antenna beam is only ten arc-minutes (about one-third of the width of the lunar disk), this new map is a mosaic of some eighteen observations. A radarmetric control between the various pieces of the mosaic was obtained via a 'beam-swing', limb-to-limb calibration. When the limb-to-limb calibration was combined with the mosaic, there were significant radar scattering differences across the maria. Eastern Mare Tranquillitatis and western Oceanus Procellarum have weaker echoes than other maria, while the central portion of Mare Serenitatis and northern Mare Imbrium have stronger echoes. There is a radar scattering difference across the southern terra as areas nearer Mare Orientale have stronger echoes than areas further from Mare Orientale.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon, and Planets (ISSN 0167-9295); 37; 59-70
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  • 4
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    Nucleus of comet Halley as a torque-free rigid rotator (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model for the rotation of the nucleus of comet Halley is proposed on the assumption that the nucleus is homogeneous and a torque-free rigid rotator. It spins about its long axis with a period of 7.4 days, while this axis precesses about a fixed direction with a period of 2.2 days. To satisfy the moments of inertia, the precession angle must be 77 deg. This model settles the major problems associated with the recent controversy about two rotation periods.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 325; 326-328
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  • 5
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    Pioneer 10 and 11 observations of waves upstream of interplanetary corotating shocks (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An extended region of enhanced magnetic field fluctuations is found upstream of some of the corotating shocks observed by Pioneer 10 and Pioneer 11 between 1 and 5 AU. This perturbed region is present when the corotating shock, generally quasi-perpendicular, becomes oblique or quasi-parallel due to a temporary out-of-spiral direction of the upstream magnetic field. The observed waves are almost not compressional. Their amplitude is a large fraction of the ambient field, and their frequency is around 1 mHz in the spacecraft frame. A brief discussion of the possible mechanisms of generation is given.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 285-290
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  • 6
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    Collisionless coupling in the AMPTE artificial comet (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Analysis of previously reported observations of the solar wind-barium interaction associated with the AMPTE artificial comet release of Dec. 27, 1984, is presented. On the basis of these results it is argued that solar wind couples momentum (and energy) to the barium ions through both laminar and turbulent processes. The laminar forces acting on the particles are the laminar electric and magnetic fields; the turbulent forces are associated with the intense electrostatic wave activity. This wave activity is shown to be caused by a cross-field solar wind proton-barium ion streaming instability. The observed wave frequencies and saturated amplitudes are consistent with the theoretical analysis.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 47-54
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  • 7
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    The ionotail of Venus - Its configuration and evidence for ion escape (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The configuration and morphology of the plasma clouds in the ionotail of Venus (revealed by the Pioneer Venus Orbiter) are studied, and the rate of planetary ion escape, which may be associated with the dissipation and removal of the ionospheric plasma, is estimated. The data supplied by the Orbiter's instruments, the Orbiter electron temperature probe, the ion mass spectrometer, the neutral mass spectrometer, the magnetometer, and the plasma analyzer, are analyzed, and the results of the observations are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 15-26
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  • 8
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    Interplanetary shock phenomena beyond 1 AU (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Attention is given to spatial dependences exhibited by spacecraft measurements obtained between 1 and 30 AU, together with temporal variations occurring between solar activity cycle maxima and minima. At 1-3 AU radial distances, shocks develop in association with the corotating solar wind streams characterizing solar minimum and accelerate solar wind evolution with distance while heating the solar wind and generating waves and turbulence. At solar maximum, shocks are observed more frequently at 1 AU but still in association with transient solar events; acceleration leading to energetic storm particles is observed both within and beyond 1 AU. The superimposed effect of large numbers of intense shocks may be responsible for the solar cycle modulation of galactic cosmic rays.
    Keywords: ASTROPHYSICS
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  • 9
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    Nucleus studies of Comet Halley (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Early results from, and research initiatives warranted by, the earth-based observations of Halley's near-nucleus and related phenomena are reviewed. Where appropriate, this information is combined with spacecraft data obtained by the various flight projects. The basic objective is to gain a greater insight into the nature of the comet's nucleus and its environment.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 12, 1; 307-316
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  • 10
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    Preliminary results of the Giotto radio science experiment (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Doppler and ranging measurements using the radio signal of the Giotto spacecraft were taken before, during, and after the encounter with Comet Halley on Mar. 13, 14, 1986. The spacecraft velocity was found to decrease by a total of 23.3 cm/s due to impacting gas and (primarily) dust in the cometary atmosphere. A preliminary dust production rate of 1000 kg/s is found to be consistent with this deceleration. Power spectra of the carrier phase fluctuations reveal an increase in level and a flattening of the spectrum just prior to encounter, presumably associated with the enhanced dust impact rate. Finally, simulated Doppler time profiles are computed using the radial dependence of plasma density observed by the Giotto in situ investigations. It is shown that the cometary electron content profile would have been clearly seen if a dual-frequency downlink radio configuration had been available at encounter.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 12, 1
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  • 11
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    A preliminary look at the dust in Comet Halley (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Highlights of infrared observations of the dust are discussed and compared with first results from the space probes. An emission feature was detected at 3.4 microns; the 10 and 20 micron silicate features were well-observed; and far-infrared data out to 160 micron were obtained. Organic material seems to be abundant in grains and may explain the 3.4 micron emission. Calculations are presented for one example of organic material. A component of the grains may volatize at temperatures around 300 K.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 12, 1; 325-334
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  • 12
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    Cometary kilometric radio waves and plasma waves correlated with ion pick-up effect at Comet Halley (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Bow-shock movements at Comet Halley are inferred from the discrete spectra of the cometary kilometric radiation (30-195 kHz); the observed emissions can be interpreted as being generated and propagating from the moving shock. The shock motion is possibly associated with the time variation of the solar wind and cometary outgassing. It is concluded that these plasma wave phenomena are manifestations of ion pick-up processes, which occur even in a remote region 7 million to 10 million km from the cometary nucleus.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 12, 1; 83-88
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  • 13
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    The Venus ionosphere (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Physical properties of the Venus ionosphere obtained by experiments on the US Pioneer Venus and the Soviet Venera missions are presented in the form of models suitable for inclusion in the Venus International Reference Atmosphere. The models comprise electron density (from 120 km), electron and ion temperatures, and relative ion abundance in the altitude range from 150 km to 1000 km for solar zenith angles from 0 to 180 deg. In addition, information on ion transport velocities, ionopause altitudes, and magnetic field characteristics of the Venus ionosphere, are presented in tabular or graphical form. Also discussed is the solar control of the physical properties of the Venus ionosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 14
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    Particulate matter in the Venus atmosphere (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The paper presents a summary of the data currently available (June 1984) describing the planet-enshrouding particulate matter in the Venus atmosphere. A description and discussion of the state of knowledge of the Venus clouds and hazes precedes the tables and plots. The tabular material includes a precis of upper haze and cloud-top properties, parameters for model-size distributions for particles and particulate layers, and columnar masses and mass loadings.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 15
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    Models of Venus neutral upper atmosphere - Structure and composition (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Models of the Venus neutral upper atmosphere, based on both in situ and remote sensing measurements, are provided for the height interval from 100 to 3500 km. The general approach in model formulation was to divide the atmosphere into three regions: 100-150 km, 150-250 km, and 250-3500 km. Boundary conditions at 150 km are consistent with both drag and mass spectrometer measurements. A paramount consideration was to keep the models simple enough to be used conveniently. Available observations are reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 16
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    CNO isotopes in red giant stars (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observational data on CNO abundance ratios in red giants and the interstellar medium (ISM) are analyzed for the implications for the production and distribution of CNO nuclides. The data included isotope abundance measurements for the atmospheres and recent ejecta of cool giants, e.g., carbon stars, S-type stars, red supergiants and oxygen-rich giants beginning an ascent of the giant branch. The contribution of intermediate-mass stars to galactic nuclear evolution is discussed after comparing red giant abundances with ISM abundances, particularly the isotopes O-16, -17 and -18. The O-12/O-18 ratios of red giants are distinctly different from those in interstellar molecular clouds. The CNO values also vary widely from the values found in the solar system.
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  • 17
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    CNO abundances in novae ejecta (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Isotope production, particularly CNO, which are enhanced in novae events and the interstellar medium (ISM) by novae are discussed in terms of emission-line data taken a few weeks after novae events. The emission-line abundances emerge only after the fading of absorption spectrum, and are also detectable in thin shells which sometimes, though rarely, form after novae. CNO abundances in these shells are equivalent to those observed in fading novae, with CNO/H ratios being 100 times solar values. Possible heavy element production pathways in the events and their shrinking are discussed, along with observation techniques for detecting CNO isotopes through absorption data on atomic transitions in novae ejecta and the ISM.
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  • 18
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    An analysis of IRAS' solar system dust bands (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of longitudinal variations in the brightness and in the latitude of the solar system dust bands recently discovered by IRAS will determine the orbital elements of the particles involved and may discriminate between cometary and asteroidal models of the origin of these bands. The expected variations for bands of dust particles with common orbital elements and small eccentricity and inclination are calculated as functions of semimajor axis.
    Keywords: ASTROPHYSICS
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  • 19
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    Mass input into and output from the meteoritic complex (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The consequences which arise from the mutual collisions occurring between interplanetary meteoroids, the Poynting-Robertson (PR) effect and the radiation pressure ejection of small meteoroids are examined. The size distribution and flux of micrometeoroids at 1 AU are derived and the dependence of spatial density on distance from the sun is established. The following conclusions are made: (1) the lifetimes of meteoroids with masses approximately greater than 0.00001 g are dominated by catastrophic collisions; (2) after bering crushed by collisions, 70 to 85 percent of this mass will be in the form of zodiacal light particles (with masses in the range of 10 to the -10th g to 10 to the -5th g) which will in part be transported by the PR effect towards the sun where they will evaporate; (3) the 15 to 30 percent of the collisional fragments which have masses approximately less than 10 to the -10th g will, for the most part, be injected into hyperbolic orbits by radiation pressure.
    Keywords: ASTROPHYSICS
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  • 20
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    Selection effects against small comets (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Everhart's (1967) formulation is used to determine the correlation between the probability of discovering a comet and the size of its nuclear radius. The analysis is concentrated on comets that are not more than two or three hundred meters in diameter; hence, heliocentric variations in cometary brightness can be neglected. The effect of cometary physical decay is also considered, and a strong observational bias against the detection of small active comets is found. The following three factors are involved: (1) small comets must pass closer to the earth than large comets in order to be detected, (2) the resulting higher angular velocity for nearby comets leads to a decrease in the time available to discover a small comet, and (3) small comets physically decay and vanish faster than do large comets.
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  • 21
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    The interplanetary micrometeoroid flux and lunar primary and secondary microcraters (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is proposed that considerable care is required to properly interpret either spacecraft in situ data or lunar crater data as well as near-earth data; in the case of the former, complications may arise which may be attributed to secondary lunar ejecta impacts, in the latter, they may result from impacting earth-orbiting debris. Experimental evidence suggests that most impact pits on lunar rocks with pit diameters smaller than 7 micrometers have been generated by lunar secondary ejecta impacts and not by primary meteoroid impacts. It is also found that lunar crater production rates are more accurate when deduced from meteoroid space experiments and not from solar flare track ages. It is concluded that in so far as all of the above qualifications are taken into account, a self-consistent meteoroid flux versus mass distribution is obtained.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 22
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    IRAS observations of the interplanetary dust emission (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Infrared Astronomical Satellite (IRAS) has completed a sensitive, highly redundant survey of the full sky in four broad photometric bands at 12, 25, 60, and 100 micrometers wavelength. The survey measured interplanetary dust emission over elongation angle ranging from 60 to 120 degrees. Bright emission from the main cloud is consistent with optically thin blackbody emission. The grains are evidently quite black, with an 'apparent albedo' of about 0.07. The data show clear evidence for deviation of the dust symmetry surface from the ecliptic plane. Surprising bands of emission were discovered near the ecliptic plane and about ten degrees on either side of it. The heliocentric distance of this material, suggested to be asteroidal in origin, is inferred to be about 2.5 AU from both color temperature and parallax measurements.
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  • 23
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    Large and small scale structures of molecular clouds in the Taurus Perseus complex (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The gaseous components studied in H I and OH absorption against the extragalactic radiosources 3C123 and 3C111 are found to be the low-density edges of condensations of a few 100 solar masses. The densest part of one of these condensations has a structure similar to that found in other dark clouds: it is fragmented into several cores of a few solar masses, with an orbital velocity dispersion of about 2 km/s. In turn, the extended low-density layer, optically thick in CO (2-1), is not a common feature. It depends on the ambient UV field, but the dust temperature in the core may control its existence. Even more critically; it is found that the lower is the dust temperature, the less massive is the core and the more extended is the envelope around it, for a given total mass in a given external pressure.
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  • 24
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    Cepheid variables as extra-galactic distance indicators (1985)
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    Publication Date: 2011-08-19
    Description: The role of Cepheid variables in establishing the inner distance scale to nearby galaxies is discussed. Emphasis is placed on the necessity for broad wavelength coverage in attempting to account for metallicity differences and reddening internal to the parent galaxies. In addition linear detectors are essential in minimizing the effects of any unresolved background contribution to the photometry. Recent infrared observations of Cepheids in Local Group galaxies are surveyed and all published data on extra galactic Cepheids are presented for convenient access.
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  • 25
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    The 50 millisecond pulsar in the Large Magellanic Cloud and the X-ray pulse emission mechanism (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: ASTROPHYSICS
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  • 26
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    Interstellar clouds - From a dynamical perspective on their chemistry (1985)
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    Publication Date: 2011-08-19
    Description: The possibility is examined that in the course of its dynamical evolution, a single mass of interstellar gas would exhibit properties of diffuse clouds, dense clouds and finally also of clouds perturbed by shocks or intense UV or X-ray radiation generated by a star of its own creation. This concept provides a common thread through the bewildering diversity of physical and chemical compositional properties shown by interstellar clouds. From this perspective, instead of being static objects, interstellar clouds are possibly incessantly evolving from initially diffuse to later dense state and then to star formation which ultimately restructures or disperses the remaining cloud material to begin the whole evolutionary process once again. Based on a simplified study of interstellar chemistry from a dynamical perspective, the ideas are presented as an heuristic: to encourage thought on the future direction of molecular astrophysics and the need to consider the chemical behavior of interstellar clouds in conjunction with, rather than in isolation from, their dynamical behavior. A physical basis must be sought for the semiempirical temperature formula which has been given a critical role in the collapse of diffuse clouds. Self-shielding effects in the chemistry of CO were neglected and this drawback should be removed; the ability of the model to explain the fractional abundances of more complex molecules, such as cyanopolyynes, should be examined.
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  • 27
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    Cometary comae (1985)
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    Publication Date: 2011-08-19
    Description: The basis of our knowledge about the structure and composition of a comet nucleus is examined. Such knowledge is inferred from observations of the cometary atmosphere (coma). However, photodissociation, photoionization, and chemistry destroy the mother molecules evaporating from the nucleus. To extract the primary information, the chemical kinetics and the physics of the coma are modeled with a computer and the results are compared with coma observations. The physics and chemistry for a dust free coma are described taking into account energy balance, multi-fluid flow for fast atomic and molecular hydrogen and the bulk fluid, and the transition from a collision dominated inner region to the free molecular flow outer region. Special attention is paid to the molecular data requirements for the current modeld and for extended models which will include solar wind interaction and dust. Such models are an important tool in support of the Giotto mission to Halley's comet, in the analysis and interpretation of coma observations, and in the understanding of the earliest history of the solar system.
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  • 28
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    Assisting extrasolar planetary detection through the determination of stellar space orientations (1985)
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    Publication Date: 2011-08-19
    Description: Various methods outlined for indirect planetary detection would greatly benefit (in some cases require) the determination of the planetary orbital plane, which is theoretically equivalent to the stellar equatorial plane. Determining the stellar space orientation, therefore, would greatly benefit extrasolar planetary detection. Stellar rotation periods determined from short-term variations in Ca II H and K sunspot emission are utilized together with both stellar radii measurements and Doppler-broadened spectral line profiles to get the stellar inclination to the line of sight. The clocklike on-the-plane-of-the-sky component determination utilizes the concentration of sunspot-associated plage areas at central stellar latitudes when viewed in Ca II H or K emission. One can perform Ca II H and K emission speckle interferometry to measure the clocklike angle of this stellar Ca II H and K emission band, modeling it as an elliptical intensity distribution. Both components should be determinable to within 10 deg for at least the resolvable fifth magnitude stars.
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  • 29
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    Problems with interpreting the radio emission from hot stars (1985)
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    Publication Date: 2011-08-19
    Description: Problems in hot star radio emission interpretation due to radio flux source and other modeling assumptions are examined. An upper limit constraint on the value of the mass loss rate divided by the constant wind velocity is imposed by assuming that the outflow is due to bremsstrahlung in a spherically symmetric wind with the stationary photosphere visible at 4500 A, and by the need for it to be less than the luminosity divided by c. The constraints are satisfied for the deduced values for OB supergiants, and to some extent for early 0 stars, but not for Wolf-Rayet stars, due to mass loss rates excessive by a factor of 10. It is suggested that the problem can be solved by postulating that part of the radio flux from Wolf-Rayet stars is due to processes in a low-density magnetized plasma.
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  • 30
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    Dynamical evolution of the Oort cloud (1985)
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    Publication Date: 2011-08-19
    Description: New studies of the dynamical evolution of cometary orbits in the Oort cloud are made using a revised version of Weissman's (1982) Monte Carlo simulation model, which more accurately mimics the perturbation of comets by the giant planets. It is shown that perturbations by Saturn and Jupiter provide a substantial barrier to the diffusion of cometary perihelia into the inner solar system. Perturbations by Uranus and Neptune are rarely great enough to remove comets from the Oort cloud, but do serve to scatter the comets in the cloud in initial energy. The new model gives a population of 1.8 to 2.1 x 10 to the 12th comets for the present-day Oort cloud, and a mass of 7 to 8 earth masses. Perturbation of the Oort cloud by giant molecular clouds in the galaxy is discussed, as is evidence for a massive 'inner Oort cloud' internal to the observed one. The possibility of an unseen solar companion orbiting in the Oort cloud and causing periodic comet showers is shown to be dynamically plausible but unlikely, based on the observed cratering rate on the earth and moon.
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    Energy conversion processes in the outer planets (1985)
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    Publication Date: 2011-08-19
    Description: Energy conversion processes which are potentially important in the outer planets at pressures greater than obut 0.1 bar are reviewed. Generation of buoyancy contrasts by condensation of various constituents is discussed with emphasis on the possible significance of phase changes in substances such as Si and Mg compounds at deep levels. It is demonstrated that, in the absence of nonequilibrium thermodynamic processes, strong kinetic energy generation must accompany the transport of heat out of the high temperature planetary interiors. The possibly dominant role of lagged parahydrogen conversion in the convective transport of heat at levels where T is less than 300 K is discussed. Measurements which may ultimately contribute to a better understanding of energy conversion processes are summarized.
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    Photochemistry and clouds of Jupiter, Saturn and Uranus (1985)
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    Publication Date: 2011-08-19
    Description: Photochemistry of ammonia, methane, phosphine, hydrogen sulfide, methylamine, hydrogen cyanide and carbon monoxide in the atmospheres of Jupiter, Saturn and Uranus is discussed. Condensation of ammonia, ammonium hydrosulfide, water, methane, ethane and acetylene below and near the tropopause of these planets is formulated. Whenever necessary, new calculations are included. Candidates for the upper atmospheric hazes, and the reddish-brown chromosphore in the clouds of Jupiter and Saturn are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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    A new emission feature in IRAS spectra and the polycyclic aromatic hydrocarbon spectrum (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: IRAS spectra of those sources which show strong 7.7 and 11.3 micron emission features also show a plateau of emission extending from 11.3 to about 13.0 microns. Like the 11.3 micron feature, this new feature is attributed to the CH out-of-plane bending mode in polycyclic aromatic hydrocarbons (PAHs). Its discovery reinforces the identification of the 'unidentified infrared emission features' as emission from PAHs. The wavelength of this new feature suggests that interstellar PAHs are not as partially hydrogenated as hitherto thought. It also constrains their molecular structure.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 299; L93-L97
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  • 34
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    Near-infrared mapping of ARP 299 (IC 694-NGC 3690) - Colliding galaxies unveiled (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Near-infrared maps and multicolor photometry of the interacting galaxies IC 694 and NGC 3690 which form Arp 299 (= Markarian 171) are presented. These data reveal for the first time the distribution of nuclei and old red stars in a cataclysmically interacting system. The nuclei are considerably offset from the visual centroids of the galaxies but not from the mass centroids. The near-infrared colors of the most active regions are strongly affected by extinction, emission form hot dust, and bremsstrahlung. Near-infrared emission is also identified with secondary regions of star formation, probably resulting from the galaxies' interaction.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 299; 896-904
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  • 35
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    Mars missions and bases - A recent look (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper discusses some of the key options for Mars programs, missions, bases, elements, and systems. Program and mission options include Mars flyby, orbiting, and landing missions; they include near-term 'sortie' missions, and later, longer-duration Mars-base missions. Key program and mission parameters include the mix of manned/unmanned elements, the number and types of space vehicles used, types of science done, trajectory options and implications launch timing and schedules, etc. The key mission parameters strongly affect the nature, sizing, and quantity of earth-to-orbit (ETO) vehicles. On-orbit assembly of space vehicles (SVs) is also an important related consideration. The potential degree of utilization of the Space Station (SS) and other then-existing elements is a key question, and several possibilities are discussed in this paper. Several configurations of SVs are provided. Several options are identified for the Mars base infra-structure, and parametric data is shown for buildup of bases as a function of mission and vehicle type. Technologies required for the missions are also discussed.
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  • 36
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    Molecular cloud evolution and star formation (1985)
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    Publication Date: 2011-08-19
    Description: The present state of knowledge of the relationship between molecular clouds and young stars is reviewed. The determination of physical parameters from molecular line observations is summarized, and evidence for fragmentation of molecular clouds is discussed. Hierarchical fragmentation is reviewed, minimum fragment scales are derived, and the stability against fragmentation of both spherically and anisotropically collapsing clouds is discussed. Observational evidence for high-velocity flows in clouds is summarized, and the effects of winds from pre-main sequence stars on molecular gas are discussed. The triggering of cloud collapse by enhanced pressure is addressed, as is the formation of dense shells by spherical outflows and their subsequent breakup. A model for low-mass star formation is presented, and constraints on star formation from the initial mass function are examined. The properties of giant molecular clouds and massive star formation are described. The implications of magnetic fields for cloud evolution and star formation are addressed.
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  • 37
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    Far-infrared and submillimeter photometry of evolved stars (1985)
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    Publication Date: 2011-08-19
    Description: Broad-band photometric observations at far infrared and submillimeter wavelengths (lambda is greater than 30 microns and less than 1) provide a unique probe of circumstellar shells in evolved objects and of the mass loss processes which produce them. The problems which these observations explore include: dust properties and dust-to-gas ratios in the outflowing material, the mass and structure of the circumstellar shell, and the pumping mechanism for maser emission. This contribution reviews the early work in this still largely unexploited field and reports results in each of the areas listed above. The dramatic advances forthcoming in this area from the IRAS satellite are previewed along with further progress which will come from the next generation of infrared and submillimeter telescopes.
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  • 38
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    Mass loss from red giants - Infrared spectroscopy (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A discussion is presented of IR spectroscopy, particularly high-resolution spectroscopy in the approximately 1-20 micron band, as it impacts the study of circumstellar envelopes. The molecular bands within this region contain an enormous amount of information, especially when observed with sufficient resolution to obtain kinematic information. In a single spectrum, it is possible to resolve lines from up to 50 different rotational/vibrational levels of a given molecule and to detect several different isotopic variants. When high resolution techniques are combined with mapping techniques and/or time sequence observations of variable stars, the resulting information can paint a very detailed picture of the mass-loss phenomenon. To date, near-IR observations have been made of 20 molecular species. CO is the most widely observed molecule and useful information has been gleaned from the observed rotational excitation, kinematics, time variability and spatial structure of its lines. Examples of different observing techniques are discussed in the following sections.
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  • 39
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    The infrared characteristics of circumstellar silicate grains (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A theoretical study of the infrared emission from circumstellar shells around late-type giants is made, with the aim of deriving the infrared characteristics of the silicate grains condensing in these shells. A large grid of models has been compared with observations of optically visible Miras, IRC sources and OH/IR stars. From fitting the observed relation between the color temperature and the strength of the 10-micron feature, it is concluded that the ratio of the 3.5 to 10-micron absorption efficiencies of the dust is about 0.25, a factor of 2 less than a previous determination. Detailed modeling of the 2 to 13-micron spectrum of OH 26.5 + 0.6, IRC + 10011 and R Cas yielded a similar ratio. These detailed models also show that the shape of the 10-micron feature, particularly around 8 and 13 microns, varies from source to source. The derived 10-micron feature is narrower for larger dust column densities. These observed differences in the intrinsic shape of the 10-micron feature are not due to differences in size of the condensing particles. Probably they are related to structural or compositional differences in the condensing silicates.
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  • 40
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    Lava tubes - Potential shelters for habitats (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Natural caverns occur on the moon in the form of 'lava tubes', which are the drained conduits of underground lava rivers. The inside dimensions of these tubes measure tens to hundreds of meters, and their roofs are expected to be thicker than 10 meters. Consequently, lava tube interiors offer an environment that is naturally protected from the hazards of radiation and meteorite impact. Further, constant, relatively benign temperatures of -20 C prevail. These are extremely favorable environmental conditions for human activities and industrial operations. Significant operational, technological, and economical benefits might result if a lunar base were constructed inside a lava tube.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 41
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    Protostellar angular momentum transport by spiral density waves (1985)
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    Publication Date: 2011-08-19
    Description: The application of rotational stability criteria to a specific model of star formation leads to the conclusion that the growth of stellar angular momentum is limited by its transfer to the disk. Excess accreted angular momentum can be transferred by torques connected with spiral density waves induced by even a slight protostellar triaxiality. In addition, viscous damping of the density waves is likely to cause the excess angular momentum to be deposited within a small region close to the protostar. Thus, it would be appropriate to treat that part of the growing protostellar disk beyond the outer Lindblad resonance as an accretion disk with a torque applied to its inner edge. It is noted that this situation is directly relevant to certain models of the evolution of the protosun and solar nebula.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 64; 435-447
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  • 42
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    Further information on structure of the atmosphere of Venus derived from the Vega Venus balloon and lander mission (1987)
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    Publication Date: 2011-08-19
    Description: Continued analysis of the pressure and temperature data returned by the two Vega mission balloons has revealed an apparently significant difference in mean atmospheric static stability between the two data sets. Furthermore, the stability is time dependent within each data set. The 6.5 K temperature contrast between the two balloons remains, and appears to have a counterpart in the contrast between two of the Pioneer Venus probes at these levels, which has been attributed to planetary scale waves. Comparisons of the Vega 2 lander data with those of the Pioneer Venus Large Probe shows relatively close agreement in the state properties and in the atmospheric static stability profiles as well.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1; 323-328
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    Meteorological variations in the middle clouds of Venus from Vega balloon in situ measurements (1987)
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    Publication Date: 2011-08-19
    Description: Instruments aboard the gondolas of the two Vega balloons obtained in situ measurements of pressure, temperature, vertical velocity relative to the balloon, cloud particle backscatter, lightning and the ambient light level. Atmospheric motions at the balloon float altitudes were also determined from earth-based tracking results. To illustrate the history of the balloon flights and to facilitate comparisons between some of the different observed quantities, measurements of pressure, temperature and backscatter are presented as time series for the entire lifetime of each balloon. Both long and short period variations have been detected. In addition, the environmental entropy encountered by each balloon will be discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    Results of the Vega 1 balloon nephelometer experiment (1987)
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    Publication Date: 2011-08-19
    Description: Backscatter nephelometer measurements obtained during the Vega 1 balloon flight are reported. During periods of minor convective activity and initial balloon ascent, the data generally agree with those obtained from other Venus mission descent probes. However, during the period of greatest convective activity experienced by the Vega 1 balloon, the signals were about a factor of two greater than any previously obtained. Although the clouds appear to be unbroken, deviations in the behavior of the detailed backscatter signals with time from those of the ambient pressure or temperature signals, especially during periods of minor convective activity, indicate much small-scale variability in cloud structure.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    Implications of the Vega balloon results for Venus atmospheric dynamics (1987)
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    Publication Date: 2011-08-19
    Description: During the Vega Venus balloon mission, data on the thermodynamic state of the atmosphere were obtained as well as wind and cloud information. Explanations are provided for the following: (1) the large amplitude atmospheric vertical winds encountered by the Vega balloons, (2) the observed 6.5 K temperature difference consistently measured between the two Vega balloons, and (3) the apparent influence of surface topography on atmospheric motions seen by the Vega-2 balloon as it flew over mountainous terrain (known as Aphrodite). It is believed that vertical winds of the magnitude encountered by the Vega-2 balloon over Aphrodite may be the result of surface-induced gravity waves.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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  • 46
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    Initial estimates of Venus winds from ground-based radio tracking of the Vega balloons (1987)
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    Publication Date: 2011-08-19
    Description: A global array of 20 radio observatories was used to measure the three-dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the Venus atmosphere by the Vega spacecraft. Initial analysis of only radial velocities indicates that each balloon was blown westward about 11,500 kilometers (8000 kilometers on the night side) by zonal winds with a mean speed of about 70 meters per second. Excursions of the data from a model of constant zonal velocity are generally less than 3-meters per second; however, a much larger variation is evident near the end of the flight of the second balloon. Consistent systematic trends in the residual for both balloons indicate the possibility of a solar-fixed atmospheric feature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    Voyager 2 plasma wave observations at Uranus (1987)
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    Publication Date: 2011-08-19
    Description: At Uranus, the Voyager 2 plasma wave investigation observed very significant phenomena related to radio emissions, dust impacts, and magnetospheric wave-particle interactions. On January 19, 1986 (R = 270 R-sub U) the plasma wave investigation detected an intense radio burst at 31 and 56 kHz, and this provided the first indication that Uranus had a magnetosphere. During the encounter, more of these sporadic bursts were observed along with relatively continuous radio emissions extending down to 10 kHz, and a sporadic narrowband radio signal with f near 5 kHz. As Voyager passed through the ring plane, the plasma wave investigation recorded a large number of dust impacts. The Voyager 2 plasma wave instrument also detected many strong electromagnetic and electrostatic plasma waves, with intensity peaks in the region within 12 Uranus radii. These waves have characteristics that can interact strongly with the local plasma and with the trapped energetic particles, leading to precipitation into the atmosphere, charged particle acceleration, and charged particle diffusion. In addition, strong wave activity was detected in the region of the bow and shock and moderate levels in the magnetic tail.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    Radio emissions from Uranus (1987)
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    Publication Date: 2011-08-19
    Description: The hardware of the Planetary Radio Astronomy Experiment aboard Voyager 2 and the results of the measurements of radio emissions from Uranus are described. Strong 40-kHz to 850-kHz radio emissions were detected after closest approach on the day-side of Uranus. The time variations of these emissions were periodic, with a period of 17.24 h closely matching that of Uranus's rotation and evidently being controlled by the strength and shape of its magnetic field. The instrument also recorded possible Uranian electrostatic discharges, vertex early arcs occurring in sequences of more than a dozen events with approximately 10-min period, and very intense isolated bursts lasting tens of minutes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1; 243-251
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    Current review of the Jupiter, Saturn, and Uranus ionospheres (1987)
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    Publication Date: 2011-08-19
    Description: The ionospheres of the major planets Jupiter, Saturn, and Uranus are reviewed in light of Pioneer and Voyager observations. Some refinements to pre-Voyager theoretical models are required to explain the results, most notably the addition of significant particle ionization from 'electroglow' and auroral processes and the need for additional chemical loss of protons via charge exchange reactions with water. Water from the Saturn rings has been identified as a major modifier of the Saturn ionosphere and water influx from satellites and/or meteorites may also be important at Jupiter and Uranus as well, as evidenced by the observed ionospheric structure and the identification of cold stratospheric carbon monoxide at Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    Neutral upper atmospheres of Venus and Mars (1987)
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    Publication Date: 2011-08-19
    Description: Results obtained over the last 21 years from satellite measurements of the neutral upper atmospheres of Venus and Mars are discussed. Particular attention is given to the chemistry of the neutral upper atmospheres of the two planets, the exospheric temperatures, and the sensitivity of their atmospheric temperatures to solar activity. Various theoretical models used to interpret the planetary atmospheric data are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    Neutral upper atmospheres of the outer planets (1987)
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    Publication Date: 2011-08-19
    Description: The major characteristics of the neutral upper atmospheres of outer planets are discussed, with special attention given to the Uranus upper atmosphere, probed by Voyager 2. The composition, thermal structure, photochemistry, and vertical mixing of the Uranus atmosphere are compared with the respective features of other outer planets. Unlike the atmospheres of Jupiter and Saturn, which reflect the solar ratios of the elements, the Uranus atmosphere was found to have only few constituents, including NH3, CH4, H2, He, C2H2, and C2H6. The eddy diffusion coefficient of Uranus, determined from occultation experiments, was found to be in the range 10,000-100,000 sq cm/sec, the lowest value amongst the major planets; this implies relatively sluggish vertical mixing. Another major difference from Saturn and Jupiter is in the fact that stable hydrocarbon products (C2H2 and C2H6) in the Uranus atmosphere begin to condense at around 5-10 mb level, resulting in the production of haze in the lower stratosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1; 79-85
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    Past and future of radio occultation studies of planetary atmospheres (1987)
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    Publication Date: 2011-08-19
    Description: Measurements of radio waves that have propagated through planetary atmospheres have provided exploratory results on atmospheric constituents, structure, dynamics, and ionization for Venus, Mars, Titan, Jupiter, Saturn, and Uranus. Highlights of past results are reviewed in order to define and illustrate the potential of occultation and related radio studies in future planetary missions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 12, 1
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    The magnetic field of Uranus (1987)
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    Publication Date: 2011-08-19
    Description: Aspherical harmonic model of the planetary magnetic field of Uranus is obtained from the Voyager 2 encounter observations using generalized inverse techniques which allow partial solutions to complex (underdetermined) problems. The Goddard Space Flight Center 'Q3' model is characterized by a large dipole tilt (58.6 deg) relative to the rotation axis, a dipole moment of 0.228 G R(Uranus radii cubed) and an unusually large quadrupole moment. Characteristics of this complex model magnetic field are illustrated using contour maps of the field on the planet's surface and discussed in the context of possible dynamo generation in the relatively poorly conducting 'ice' mantle.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 15329-15
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    Survey of electrons in the Uranian magnetosphere - Voyager 2 observations (1987)
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    Publication Date: 2011-08-19
    Description: Results of an analysis of the Voyager 2 plasma-science-experiment electron measurements made during the Uranus encounter are presented. The energy coverage is in the range of 10 to 5950 eV. The large day-night asymmetry together with the spin axis alignment with the solar direction and the large tilt of the planetary magnetic dipole suggest that solar-wind-driven time-dependent magnetospheric convection will be an important transport mechanism within the Uranian magnetosphere. The steady state convection time of the plasma is estimated to be between 1 and 3 days.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 15263-15
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    Surface waves on Uranus' magnetopause (1987)
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    Publication Date: 2011-08-19
    Description: Uranus' magnetosphere has a well-developed, thick magnetopause that was fully traversed twice by Voyager 2, once inbound to the planet and once outbound. This boundary appears to resemble earth's magnetopause in approximate shape and even to the extent of supporting surface waves which were observed on the inbound pass at a distance of 18.3 Uranus radii. There were apparently eight partial transitions from the magnetosheath into the current sheet of the magnetopause at this time, followed by a final complete transition to the magnetosphere. Six of the estimated normal vectors to the local boundary show clear evidence of oscillations in the slope with typical angular excursions, from one partial transition to the next, of about 90 deg. The vectors oscillated approximately in a plane that was severely tilted by about 49 deg with respect to Uranus' orbital plane.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 15347-15
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    Ordinary mode radio emission from Uranus (1987)
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    Publication Date: 2011-08-19
    Description: On Jan. 24, 1986, during the inbound trajectory to Uranus, the planetary radio astronomy instrument on Voyager 2 detected left-hand-polarized emission for several hours at frequencies near 200 kHz. Unlike the dominant source observed on the nightside of the planet, only a single episode of this inbound emission was seen, and the emission was extremely weak. Generating less than 500 kW, it is probably the weakest freely propagating planetary radio emission thus far observed by Voyager. This weak emission is associated with a source region in the vicinity of the north (dayside) magnetic pole of Uranus, where magnetic-field lines point approximately in the direction of the spacecraft when the emission is observed. Therefore the wave normal angle relative to B is probably less than 90 deg in the generation region. It is concluded that direct wave generation in the magnetoionic ordinary mode is most likely. The source location for this emission is consistent with a region magnetically conjugate to the dominant nightside source, which is located in the vicinity of the south magnetic pole. The ordinary mode emission is discussed in the context of the electron-cyclotron maser mechanism.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 15211-15
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    Uranus satellites - Densities and composition (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Homogeneous and core-differentiated silicate/ice models of the Uranian satellites Miranda, Ariel, Umbriel, Titania, and Oberon are examined in the light of imaging observations and mass and density determinations obtained during the Voyager 2 encounter with Uranus in January 1986. The data and model predictions are compared in extensive tables and graphs and discussed in detail. The mass fractions of silicates in Oberon and Titania are found to be between 0.42 and 0.65, about the same as the average for the satellites of Jupiter and Saturn but significantly higher than that for the smaller Saturnian satellites or that predicted by current solar-nebula models. It is suggested that the satellites formed by accretion of material from their primary planets' outer envelopes. The observed rock/ice fractions are attributed to solar-nebula CO and solid-organics abundances and to preferential dissolution of H2O in outer-envelope planetesimals.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 14884-14
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    Isotopic analysis of basaltic fragments from lunar breccia 14321 - Chronology and petrogenesis of pre-Imbrium mare volcanism (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Internal (mineral) Rb-Sr isochrons were determined for six Apollo 14 mare basalts of lunar breccia 14321. The ages of these fragments, which represent the time of crystallization of the respective mafic lavas, range from about 4.05 to 4.24, and, possibly, to 4.33 Ga and are among the oldest dates reported for mare basalts. For three of the fragments, internal Sm-Nd isochron data were collected and initial Nd isotopic composition was determined. The results are discussed with reference to the original source of these different basaltic fragments.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 51; 3241-325
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  • 59
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    Are small diamonds thermodynamically stable in the interstellar medium? (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Very small diamond particles (50 A diameter) are shown to be thermodynamically stable with respect to similar sized graphite particles for reasonable values of the surface free energies of diamond and graphite. Small diamonds are likely to be stable against both thermal evaporation and chemical attack in the general interstellar medium. A few of the consequences of these conclusions are examined.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 139; 1, De
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    The ultraviolet variability of AY Ceti (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: AY Cet is a single-line binary comprised of a spotted G5 III primary and a white dwarf secondary. A series of UV spectra have been obtained with the IUE satellite on five different dates covering a substantial part of the optical cycle of the primary star. No evidence that the continuum or the Ly-alpha absorption line of the secondary star varied is found. There were significant changes in the strengths of the UV emission lines, but the variations were only weakly correlated with either the orbital phase of the binary or the rotational phase of the primary. The UV emission lines were especially strong near maximum visual brightness at a time when the starspot(s) on the primary was least visible. The enhanced line emission is attributed to a flare event on the primary, most likely at a high-latitude site close to the pole of this star. The UV radiative losses of this flare were comparable with those of flares previously observed on the RC CVn variables Lambda And and HR 1099.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 94; 1657-166
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  • 61
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    On the saturation of the refractive index structure function. II - Influence of the correlation length on astronomical 'seeing' (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A physical length scale in the wavefront corresponding to the parameter (r sub 0) characterizing the loss in detail in a long exposure image is identified, and the influence of the correlation scale of turbulence as r sub 0 approaches this scale is shown. Allowing for the effect of 2-point correlations in the fluctuations of the refractive index, Venkatakrishnan and Chatterjee (1987) proposed a modified law for the phase structure function. It is suggested that the departure of the phase structure function from the 5/3 power law for length scales in the wavefront approaching the correlation scale of turbulence may lead to better 'seeing' at longer wavelengths.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 229; 379-382
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  • 62
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    Microturbulence in the upper photosphere of Alpha Persei (F5 Ib) derived from ultraviolet spectral observations (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High-resolution ultraviolet spectra of the moderate supergiant Alpha Per (F5 Ib) were studied to determine the dynamic state of its upper photosphere. It was found that the line-of-sight microturbulent velocity component in the region of origin of the UV spectrum is about 5 km/s, and is slightly smaller than the value derived from the visual spectrum. This is ascribed to dissipation of mechanical energy between the higher and lower layers where, respectively, the ultraviolet and visual light lines originate. Between these two levels, which are one scale height apart, the mechanical energy flux decreases to about 0.3 of its photospheric value. The consequent value for the (outward directed) turbulent acceleration is 24 cm/sec-squared, more than one half the observationally determined effective acceleration of gravity.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 185; 1-2,
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  • 63
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    Deconvolution of a pre-outburst picture of SN 1987A (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The block iterative method (Young 1971) of algebraic image restoration is applied to a photographic plate of the field around SN 1987A obtained 4 yr before outburst by Chu at the CTIO 4-m telescope. By setting appropriate constraints for the solution on a pixel-by-pixel basis, the image of a starfield centered on Sk -69 202, the precursor to the supernova, is restored. It is found that this star has two companions, which others (e.g., Walborn et al., 1987 and West et al., 1987) have also noted and designated as Star 2 and Star 3. Also found is marginal evidence for Star 4, a weak source at theta = 222 deg, r = 1.9 arcsec. Correction for the contributions of these companions yields an estimate of the magnitude for Sk -69 202 alone of V = 12.37.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 185; 1-2,
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  • 64
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    Helium diffusion in stars and the value of the cosmological constant (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The effect of He diffusion on the evolution of stars is to speed it up by increasing the mean atomic weight at the center, thereby minimizing the apparent conflict between the great ages of globular clusters and the age of the universe, as arrived at via the Hubble constant. Attention is presently given to the consequences of work on this effect by Noerdlinger and Arrigo (1980) and Stringfellow et al. (1983), implying that Tayler's (1986) estimate for globular clusters of 16 Gyr should be reduced to 13 Gyr.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Quarterly Journal (ISSN 0035-8738); 28; 345
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  • 65
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    Radiometry of Deimos (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ground-based infrared photometry of Deimos at 4.8, 10, and 20 microns is reported. The observed fluxes are significantly brighter than predicted by the 'standard' thermal model. Recent recalibrations that modify the model beam pattern of the infrared emission are marginally consistent with the observations at 10 and 20, but not at 4.8 microns.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal (ISSN 0004-6256); 94; 1361-136
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  • 66
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    Particle acceleration and production of energetic photons in SN1987A (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A pulsar wind model for the acceleration of particles in SN1987A is discussed. The expected photon flux is investigated in terms of the spectrum of parent protons and electrons, the nature of the region in which they propagate after acceleration, and the magnetic field and radiation environment which determines the subsequent fate of produced photons. The model is found to produce observable signals if the spin period of the pulsar is 10 ms or less.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 329; 314-316
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  • 67
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    Observations of jets from low-luminosity stars. II - SVS 12, HH 30, near HL Tauri, and HH 34 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Spatially resolved spectral scans were obtained for four Herbig-Haro jets emanating from low-luminosity premain-sequence stars. There appears to be a general tendency for the excitation and electron density to diminish along these jets. For three jets, the electron density dependence is close to 1/r. HH 30's scattered stellar continuum showed much weaker Fe II lines in 1985 than in 1979, indicative of variable stellar activity. The most distant knot in HH 34's jet has the lowest excitation of any known HH object, with S II-line/H-alpha = 12.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 321; 846-854
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  • 68
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    The unusual radio outburst of Nova Vulpeculae 1984 No. 2 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Multifrequency radio monitoring of Nova Vulpeculae 1984 No. 2 has revealed a unique radio light curve, exhibiting a strong outburst which precedes the appearance of normal radio emission from the principal ejecta of the nova by at least 100 days. The early emission is extremely optically-thick and has brightness temperature in excess of 100,000 K. A model is discussed in which the radiation is produced by a strong shock propagating outward through the principal ejecta of the nova, as a result of an interaction with a later, high velocity wind from the central source. It is shown that the general features of the radio light curve can be explained by the presence of a central wind with a mass loss rate of about 0.00001 solar masses/yr, lasting for a period of 200 to 300 days after the optical outburst. The first radio map of nova ejecta shortly after outburst is presented. Comparison of the angular expansion rate to the ejection velocity implies a distance of 3.6 kpc, and preliminary analysis of the main outburst emission indicates a mass and kinetic energy of the ejecta respectively of about 0.0008 solar masses and 8 x 10 to the 45th erg.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 183; 1, Se
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  • 69
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    Refractory interplanetary dust particles (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Criteria are described by which refractory interplanetary dust particles (IDPs) can be differentiated from the products of spacecraft debris. These criteria have been used to discover and characterize IDPs that are composed predominantly of refractory phases. Two of these particles contain hibonite, perovskite, spinel, refractory glass, and a melilite; only hibonite was identified within a third. The grain size for all particles ranges from 0.05 to 1 micrometer, so that they are much finer grained than the refractory calcium- and aluminum-rich inclusions in meteorites. The glass-containing refractory IDPs may be primitive nebular condensates that never completely crystallized and thus have been preserved extant.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 237; 1466-146
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  • 70
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    Observable properties of E0 triaxial galaxies - A test for triaxiality (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is shown that most triaxial galaxies oriented in space to appear as E0 galaxies should have observable rotation velocities. By projecting Levison and Richstone's (1987) triaxial models so that they look like E0s, it was found that v/sigma can be as large as 1.0. In a separate argument, the observed distribution of axial ratios of ellipticals was used to show that between 3 percent and 23 percent of E0 galaxies are intrinsically flattened systems. Thus, if elliptical galaxies are triaxial then some E0 galaxies should have observable rotation velocities.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 320; L93-L97
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  • 71
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    Polyoxymethylene in Comet Halley (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is shown that polyoxymethylene (POM) with n about four or five explains the mass spectrum obtained with the PICCA instrument during the Giotto encounter with Comet Halley. A sequence of processes is presented showing the likelihood that POM will form under interstellar conditions. A preliminary comet coma model that includes POM is presented which predicts a qualitatively correct spectral intensity behavior when compared with observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 320; L149-L15
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  • 72
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    Spectral signatures of jumps and turbulence in interplanetary speed and magnetic field data (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is shown here that, consistent with a suggestion of Burlaga and Mish (1987), the f exp -2 spectra in the magnitudes of the magnetic and velocity fields in the solar wind result from jumps due to various rapid changes in the time series for these quantities. If these jumps are removed from the data, the spectra of the resulting 'difference' time series have the f exp -5/3 form. It is concluded that f exp -2 spectra in these magnitudes arise from phase coherent structures that can be distinguished clearly from incoherent turbulent fluctuations.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 10
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  • 73
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    Detection of a hot plasma component within the core regions of Jupiter's distant magnetotail (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Voyager-2 PLS low-energy plasma data and the magnetometer data are combined with the the LECP ion data (E greater than 28 keV) for the distant magnetotail observations (R = 5000-9000 Jupiter radii). A definite enhancement of LECP fluxes within the core regions (where the PLS densities and magnetic-field pressure are lower than in the surrounding regions) is shown, indicating that this hot tenuous plasma is present within the core regions. In general there is a strong anticorrelation between PLS density and LECP fluxes, while a less pronounced anticorrelation between magnetic-field pressure and LECP fluxes is observed. Estimates of LECP pressures suggest that this hot plasma can provide the previously described missing pressure in the core if heavy ions dominate the ion composition. The angular dependence of the LECP data indicates a flow of this hot plasma in the anti-Jupiter direction. This outflowing plasma could be the remnant of the magnetospheric wind observed near Jupiter by LECP. On the basis of this preliminary study, the core regions are found to have similarities to a plasma sheet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 9943-994
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  • 74
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    Light scattering in cometary dust comae (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Single and multiple scattering calculations were performed for a spherically symmetric cometary atmosphere irradiated by a plane parallel source. It is suggested that the increased flux found for anisotropic phase functions is due to the effect of directional scattering in the forward sun-comet axis. The isotropic multiply scattered flux at the surface is shown to be an increasing function of the opacity (tau) for tau of less than about 2.5. At large tau values, the maximum in the downward directed scattered flux still increases, but occurs at a height of several radii above the nucleus, resulting in a reduction at the surface. Results suggest that, except in the vicinity of the sun-comet axis, the plane parallel geometry tends to underestimate the degree of scattering.
    Keywords: ASTROPHYSICS
    Type: Earth, Moon, and Planets (ISSN 0167-9295); 39; 51-74
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  • 75
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    Shock effects and argon loss in samples of the Leedey L6 chondrite experimentally shocked to 29-70 GPa pressures (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The recovery of polished 600-micron-thick 7-mm-diameter disk samples and powder samples of the Leedey L6 chondrite from 29-70-GPa experimental shocks is investigated experimentally under vacuum conditions, with a focus on the possible direct shock loss of radiogenic Ar. The results of petrographic examination of the shocked samples and Ar isotope measurements are presented in tables, graphs, and micrographs and characterized in detail. The principal damage mechanisms are identified as mechanical disaggregation and increasing cataclasis, with little melting. The degassing of radiogenic Ar is found to be relatively modest and to increase with shock pressure and sample porosity; it is attributed to a combination of mechanical grain disruption and feldspar melting. It is inferred that Ar loss in naturally shocked materials (especially those showing few signs of melting) probably occurs during extended exposure to high temperatures during impact formation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 51; 2035-204
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    Optical efficiencies of lightning in planetary atmospheres (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first simulations of lightning in planetary atmospheres by laser-induced plasmas are reported. These simulations show that the fraction of the energy in lightning discharge channels that is radiated in the visible spectrum is similar for earth, Venus, and Titan, but quite different for Jupiter. One implication of these results is that the amount of trace gases produced by lightning in the Jovian atmosphere must be larger than previously estimated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 328; 509
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  • 77
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    Count Bowell at record heliocentric distance (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: New observations of Comet Bowell at the record distance of 13.6 AU are presented. An extended coma is present, the size of which is consistent with the same slow expansion rate of roughly 1 m/s detected around perihelion. The cross-section of the solid grains within the central 10 arcsec of the coma has decreased by over an order of magnitude since 1980-84, which indicates that the coma production is declining. The decline began near R of roughly 10 AU, the same distance at which production began on the preperihelion leg. The coma at R of 10 AU or less may be formed by sublimation of CO2 or an ice of similar volatility from the nucleus.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 328; 506-509
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  • 78
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    Formation of large-scale structure from cosmic-string loops and cold dark matter (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Some results from a numerical simulation of the formation of large-scale structure from cosmic-string loops are presented. It is found that even though G x mu is required to be lower than 2 x 10 to the -6th (where mu is the mass per unit length of the string) to give a low enough autocorrelation amplitude, there is excessive power on smaller scales, so that galaxies would be more dense than observed. The large-scale structure does not include a filamentary or connected appearance and shares with more conventional models based on Gaussian perturbations the lack of cluster-cluster correlation at the mean cluster separation scale as well as excessively small bulk velocities at these scales.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 328; 691-694
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    Orbital eccentricity in classical novae (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The effect on the orbital parameters of a classical nova of the ejection of mass during the nova explosion is considered. The most easily observable consequence is the generation of a small eccentricity in the orbit which leads to a luminosity modulation at a period just longer than the orbital period. Observation of such an effect would have implications not just for interpreting the dynamics of the explosion but also for measuring the secular effect of tidal interaction after the outburst.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 328; 505
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  • 80
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    Regularly pulsed neutrinos from supernova SN1987A? (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Some consequences of the 8.9 millisecond periodicity observed in neutrino events from SN1987A with the Kamiokonde and IMB experiments are discussed. Interpreting the apparent period as a rotation of a compact object would imply that the neutrino emission is anisotropic and that the neutrino mass, averaged over all observed flavors, is less than 0.2 eV/c-squared. It is also noted that P = 8.9 ms is a reasonable period for very young pulsars.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 328; 503
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    Nonspherical supernova remnants. IV - Sequential explosions in OB associations (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Multisupernova remnants, driven by sequential supernova explosions in OB associations, are modelled by means of two-dimensional hydrodynamical calculations. It is shown that due to the Rayleigh-Taylor instability the remnants quickly evolve into highly irregular structures. A critical evaluation of the multisupernova model as an explanation for supershells is given.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 182; 1, Au; 120-126
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    Evolutionary sequences for horizontal branch stars (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new grid of canonical evolutionary horizontal branch (HB) sequences is presented. Sequences are computed for each combination of the following helium and heavy-element abundances, respectively: Y(main sequence) = 0.20, 0.25, 0.30, and Z = 0.0001, 0.001, and 0.01. The results show that the bifurcation point at which the HB morphology changes from redward-evolving tracks to tracks with blueward loops shifts to higher effective temperatures with increasing helium abundance or metallicity. The sequences can be used to study in more detail how a number of HB properties such as the HB lifetime, the effective temperature at the bifurcation point in the track morphology, the luminosity dropoff of the blue HB, and the luminosity width of the red HB depend on the composition.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 65; 95-135
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  • 83
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    Landform identification in lunar radar images (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Lunar radar images have been investigated in order to understand how various radar parameters affect landform identification. The high-resolution (1-2 km cell size) 3.8-cm images of Zisk et al. (1974) were used along with the low and high resolution 70-cm mosaics of Thompson (1974 and 1987). The results indicate that radar cell size is the single most important radar parameter and that lunar features are likely to be correctly identified if they are longer than an 'identification resolution' of five times the radar cell size. The moon is considered here as an analog of Venus, since the two planets have similar mean scattering behavior.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 84
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    Shock processing of interstellar dust - Diamonds in the sky (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The processing of interstellar dust grains by strong shock waves is studied, with the emphasis on the effects of grain-grain collisions. Such collisions provide the high pressures required to transform interstellar graphite and amorphous carbon grains into diamonds. Diamond metamorphism is as important for the destruction of such grains as vaporization and sputtering. It is calculated that about 5 percent of the C is expected to be in the form of 5-100 A diamonds in the interstellar medium. These results support the suggested interstellar origin for the recently discovered small meteoritic diamonds by providing a feasible interstellar formation mechanism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 319; L109-L11
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    Quantized synchrotron radiation in strong magnetic fields (1987)
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    Publication Date: 2011-08-19
    Description: Spectra from electrons making synchrotron transitions in high magnetic fields are calculated using the exact quantum transition rates for Landau states up to n = 500, and the results are compared with spectra calculated from the classical formula and the asymptotic quantum formula. The behavior of the transition rates are examined at low and high harmonics as a function of the spin state of the electron. The calculations confirm those of Herold, Ruder, and Wunner (1982) for low Landau states, extending them to higher states and individual spin state transitions. The results also confirm the dominance of ground-state transitions at high field strengths noted by White (1976). Single particle emissivities for electrons with both spin-up and spin-down in the initial state are calculated using these transition rates. Spectra for thermal electron distributions at transrelativistic temperatures and for steady state injection of monoenergetic electrons with isotropic pitch angles are also presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 319; 939-950
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    Molecular and atomic clouds associated with infrared cirrus in Ursa Major (1987)
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    Publication Date: 2011-08-19
    Description: Observations of CO and H I revealed that in Ursa Major the high-latitude far-infrared 'cirrus' emission discovered by the Infrared Astronomical Satellite comes from molecular and atomic clouds. These clouds differ sufficiently from the large clouds in the Galactic plane so that the ratio of H2 column density to velocity-integrated CO radiation temperature, N(H2)/W(CO), derived from Galactic plane surveys, may not apply to them. On the assumption of a constant gas-to-dust ratio, it is argued that the cirrus emission in Ursa Major is a good mass tracer, since both the atomic and the molecular gas are probably optically thin at visual wavelengths, and the grains are heated not by local sources but by the background field of Galactic starlight. The N(H2)/W(CO) ratio thus derived for those diffuse clouds, is significantly lower than the ratio applicable to Galactic plane surveys.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 319; 723-729
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    Investigation of Martian H2O and CO2 via orbital gamma ray spectroscopy (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The capability of an orbital gamma ray spectrometer to address presently unanswered questions concerning H2O and CO2 on Mars is investigated. The gamma ray signal produced by the Martian atmosphere and by several simple models of Martian surface materials is calculated. Results are reported for: (1) the production of neutrons in the atmosphere and in the subsurface material by cosmic ray interactions, (2) the scattering of neutrons and the resultant neutron energy spectrum and spatial distributions, (3) the reproduction of gamma rays by neutron prompt capture and nonelastic scatter reactions, (4) the production of gamma rays by natural radionuclides, (5) the attenuation of the gamma ray signal by passage through surface materials and the Martian atmosphere, (6) the production of the gamma ray continuum background, and (7) the uncertainty in gamma ray line strengths that results from the combined signal and background observed by the detector.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 9153-916
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    Numerical simulation of the generation of turbulence from cometary ion pick-up (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of magnetic field fluctuations near Comet Halley have revealed a rapid development of a Kolmogoroff-like turbulence spectrum extending from below 0.01 Hz to above 0.1 Hz. Spectra obtained far from the comet have a strong peak in power near the Doppler-shifted ion-cyclotron frequency of singly ionized water. Closer to the comet, the spectrum at higher frequencies is enhanced in power level over the background solar wind spectrum by approximately an order of magnitude. The equations of incompressible MHD are solved using a two-dimensional 256 x 256 mode spectral method code to simulate this spectral evolution as an inertial range turbulent cascade. The initial conditions contained a constant magnetic field and a single coherent wave mode at a low wave number. The solar wind turbulence was modeled by a background noise spectrum having a Kolmogoroff spectral index. The coherent mode decayed into an inertial range spectrum with Kolmogoroff slope within a few eddy-turnover times. Both the time scale and the increase in power level of the turbulence seen in the simulation are in accord with the Giotto observations.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 14; 860-863
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  • 89
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    IRAS observations of southern molecular clouds (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A report is given of a project to use IRAS Band 3 (60 microns) and Band 4 (100 microns) observations to investigate the far-infrared properties of southern galactic molecular clouds. A method by which dust temperature and total gas column density can be estimated is presented. Results are tabulated for 65 prominent southern far-infrared sources. The dust temperatures are closely grouped between 30 and 50 K, while the column densities range between 2 x 10 to the 20th and 10 to the 22nd/sq cm. Maps of dust temperature and gas column density have been generated for two fields containing far-infrared sources to illustrate the effectiveness of this form of presentation.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 227; 1013-102
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  • 90
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    X-ray spectra and atmospheric structures of bursting neutron stars (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Atmospheric structures and emitted X-ray spectra of bursting neutron stars are investigated. Theoretical curves are fitted to observational ones on the color temperature vs. luminosity diagram and two relations among mass, radius, and distance of the bursters are obtained. The fit of the theoretical curve to observations is statistically acceptable. Two possible sets of mass, radius, and distance to the X-ray bursts source MXB 1636-536 are derived, taking into account absorption lines at 4.1 keV, theoretical mass-radius relations of neutron star models, and the distance to the Galactic center. If the absorption line is due to Cr XX III, then M = 1.7-2.0 solar masses, R = 11-12 km, and d = 6.3-6.7 kpc, and if it is due to Fe XXV, then M = 1.8-2.1 solar masses, R = 8-10 km, and d = 5.8-6,4 kpc. The distance to the Galactic center is almost the same as that to MXB 1636-536.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of Japan, Publications (ISSN 0004-6264); 39; 2, 19; 287-308
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  • 91
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    Optical and UV spectroscopy of the black hole binary candidate LMC X-1 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Both further optical spectroscopy of the binary star identified with LMC X-1, obtained between 1983 and 1985, and a series of IUE UV spectra taken during a 5 day interval in 1984 are presented. The optical data are used to refine the orbital period to 4.2288 days, and improved orbital parameters are derived. The velocity of the optical emission lines is antiphased with the absorption lines and has twice the velocity amplitude. These new results support the estimates of the masses in the system given earlier. The most probable component masses are approximately 20 solar masses for the primary and near 6 solar masses (for the x-ray star), suggesting the the latter may be a black hole. The UV spectra show very weak, low-velocity stellar-wind lines. It is suggested that much of the surrounding medium is highly ionized by the X-ray flux. The 'nonwind' UV spectral lines and the UV continuum temperature are consistent with the optical data, indicating a late O type star of M(bol) = -8.5. There is a weak modulation of absorption-line strengths with orbital phase, suggestive of a lack of axisymmetry in the X-irradiation of the primary star and indicative of a fairly low orbital inclination.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 94; 340-344
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  • 92
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    Comparison of the compositions of Venusian surface rocks with those of the terrestrial ocean floor (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A statistical comparison of data on the composition of the Venusian surface obtained with Venera and Vega lander X-ray fluorescence spectrometers and data on the composition of the terrestrial ocean floor indicates that the Venera 14 data correspond to certain thoeiitic basalts of the Kane fracture zone in the Middle-Atlantic ridge (22-25 deg N). It is suggested that deep magma storage regions exist on Venus and that the separation of tholeiitic and alkali magmas from a single primitive parent magma is an important process on Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomicheskii Vestnik (ISSN 0320-930X); 21; 122-135
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  • 93
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    Planning the Voyager spacecraft's mission to Uranus (1987)
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    Publication Date: 2011-08-19
    Description: The application of the systems engineering process to the planning of the Voyager spacecraft mission is described. The Mission Planning Office prepared guidelines that controlled the use of the project and multimission resources and spacecraft consumables in order to obtain valuable scientific data at an acceptable risk level. Examples of mission planning which are concerned with the design of the Deep Space Network antenna, the uplink window for transmitting computer command subsystem loads, and the contingency and risk assessment functions are presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Irish Astronomical Journal (ISSN 0021-1052); 18; 40
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  • 94
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    The hydrogen coverage of interstellar PAHs (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The rate at which the CH bond in interstellar Polycyclic Aromatic Hydrocarbons (PAHs) rupture due to the absorption of a UV photon has been calculated. The results show that small PAHs (less than or equal to 25 carbon atoms) are expected to be partially dehydrogenated in regions with intense UV fields, while large PAHs (greater than or equal to 25 atoms) are expected to be completely hydrogenated in those regions. Because estimate of the carbon content of interstellar PAHs lie in the range of 20 to 25 carbon atoms, dehydrogenation is probably not very important. Because of the absence of other emission features besides the 11.3 micrometer feature in ground-based 8 to 13 micrometer spectra, it has been suggested that interstellar PAHs are partially dehydrogenated. However, IRAS 8 to 22 micrometer spectra of most sources that show strong 7.7 and 11.2 micrometer emission features also show a plateau of emission extending from about 11.3 to 14 micrometer. Like the 11.3 micrometer feature, this new feature is attributed to the CH out of plane bending mode in PAHs. This new feature shows that interstellar PAHs are not as dehydrogenated as estimated from ground-based 8 to 13 micrometer spectra. It also constrains the molecular structure of interstellar PAHs. In particular, it seems that very condensed PAHs, such as coronene and circumcoronene, dominate the interstellar PAH mixture as expected from stability arguments.
    Keywords: ASTROPHYSICS
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  • 95
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    Photometric light curves for seven rapidly-rotating K dwarfs in the Pleiades and Alpha Persei clusters (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Light curves and period estimates were obtained for several Pleiades and Alpha Persei cluster K dwarfs which were identified as rapid rotators in earlier spectroscopic studies. A few of the stars have previously-published light curves, making it possible to study the long-term variability of the light-curve shapes. The general cause of the photometric variability observed for these stars is an asymmetric distribution of photospheric inhomogeneities (starspots). The presence of these inhomogeneities combined with the rotation of the star lead to the light curves observed. The photometric periods derived are thus identified with the rotation period of the star, making it possible to estimate equatorial rotational velocities for these K dwarfs. These data are of particular importance because the clusters are sufficiently young that stars of this mass should have just arrived on the main sequence. These data could be used to estimate the temperatures and sizes of the spot groups necessary to produce the observed light curves for these stars.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99; 471-481
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  • 96
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    Modeling the Milky Way in the infrared (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spatial distribution of stars in the Milky Way is modeled using an exponential disk with the addition of a de Vaucouleurs (1958, 1977, and 1979) R exp 1/4 spheroid. The present model is compared to 2-2.5-micron star counts and surface-brightness data and to IRAS 12-micron source counts. The data are consistent with a flattened bulge; it is maintained that a fraction of the bulge population has a considerable infrared excess.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99; 453-460
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  • 97
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    Evolutionary models of interstellar chemistry (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The goal of evolutionary models of interstellar chemistry is to understand how interstellar clouds came to be the way they are, how they will change with time, and to place them in an evolutionary sequence with other celestial objects such as stars. An improved Mark II version of an earlier model of chemistry in dynamically evolving clouds is presented. The Mark II model suggests that the conventional elemental C/O ratio less than one can explain the observed abundances of CI and the nondetection of O2 in dense clouds. Coupled chemical-dynamical models seem to have the potential to generate many observable discriminators of the evolutionary tracks. This is exciting, because, in general, purely dynamical models do not yield enough verifiable discriminators of the predicted tracks.
    Keywords: ASTROPHYSICS
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  • 98
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    Optical observations related to the molecular chemistry in diffuse interstellar clouds (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations, which have been published since 1979, of molecular species in diffuse clouds are discussed. Particular attention is given to the ultraviolet measurements of CO with the Copernicus and IUE satellites and to ground-based optical measurements of CH, CH(+), CN, and 02. These data encompass large enough samples to test the chemical schemes expected to occur in diffuse clouds. Upper limits for other species (e.g., H2O, H2O(+), and C3) place restrictions on the pathways for molecular production. Moreover, analysis of the rotational distribution of the C2 molecule results in the determination of the physical conditions of the cloud. These parameters, including density, temperature, and the intensity of the radiation field, are necessary for modeling the chemistry.
    Keywords: ASTROPHYSICS
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  • 99
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    The fate of the earth in the red giant envelope of the sun (1987)
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    Publication Date: 2011-08-19
    Description: The effect on the earth of entering the red giant envelope of the future sun is studied. Employing a 30-zone red giant model, the earth orbital decay timescale, neglecting ablation/vaporization, is determined to be of the order of 200 years, rendering earth survival impossible. The effects of ablation/vaporization processes are found to increase the ballistic coefficient of earth, thereby setting the 200-year decay timescale as an upper limit.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 178; 1-2,
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  • 100
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    Thermal diffusion in partially ionized gases - The case of unequal temperatures (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Previous calculations of thermal diffusion coefficients in partially ionized gases are extended to the case of unequal neutral and ion temperatures and/or temperature gradients. Formulas are derived for the general case of a major gas as well as for minor atoms and ions. Strong enhancements of minor-ion thermal diffusion coefficients over their values in the fully ionized gas are found when the degree of ionization in the main gas is relatively low. However, compared to the case of equal temperatures, the enhancements are less strong when the neutrals are cooler than the ions. The specific case of the H-H(+) mixture, which is important in the study of solar and stellar atmospheres, is discussed as an application.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 178; 1-2,; 286-291
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