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  • Other Sources  (14)
  • 1
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    Spectroscopic evidence for interstellar ices in comet Hyakutake (1996)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Volatile compounds in comets are the most pristine materials surviving from the time of formation of the Solar System, and thus potentially provide information about conditions that prevailed in the primitive solar nebula. Moreover, comets may have supplied a substantial fraction of the volatiles on the terrestrial planets, perhaps including organic compounds that played a role in the origin of life on Earth. Here we report the detection of hydrogen isocyanide (HNC) in comet Hyakutake. The abundance of HNC relative to hydrogen cyanide (HCN) is very similar to that observed in quiescent interstellar molecular clouds, and quite different from the equilibrium ratio expected in the outermost solar nebula, where comets are thought to form. Such a departure from equilibrium has long been considered a hallmark of gas-phase chemical processing in the interstellar medium, suggesting that interstellar gases have been incorporated into the comet's nucleus, perhaps as ices frozen onto interstellar grains. If this interpretation is correct, our results should provide constraints on the temperature of the solar nebula, and the subsequent chemical processes that occurred in the region where comets formed.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Nature (ISSN 0028-0836); Volume 383; 6599; 418-20
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  • 2
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    Multiwavelength observations of RV Tauri stars. 4: SX Centauri (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We present ultraviolet, optical and infrared observations of the RV Tauri star SX Cen. From a fit of model atmospheres to the data we conclude that Z/Z solar = 0.033, that SX Cen has an extended atmosphere, and that the spectral types implied by the ultraviolet data close to deep minimum are consistent with those implied from optical spectra. Unlike AC Her, there seems to be no silicate component in the circumstellar dust shell, and the star pulsates in purely radial modes. The implication is that, despite their many similarities, SX Cen seems to be at a significantly earlier phase of post-AGB evolution than AC Her. Additional data, particularly in the infrared, are necessary to confirm this conclusion.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 292; 1; p. 102-114
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  • 3
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    The reddening and variability of XX Ophiuchi (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We present polarization data on the XX Oph system which suggest that the interstellar extinction to this object has been overestimated in the past: our data imply A(V) = 1.6 mag. Our photometry and infrared spectroscopy suggest a spectral class of M7III for the late component, and a BOV companion that ionizes the wind of the cool component. XX Oph seems more like a Zeta Aur/VV Cep system than a 'symbiotic object'. The photometric variability of XX Oph seems to have a number of causes, ranging from shell-type variability in the U band to variations in the M component in the infrared.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 267; 1; p. 161-167.
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  • 4
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    A strong 3.4 micron emission feature in comet Austin 1989c1 (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High resolution 2.8-4.0 micron spectra of the 'new' comet Austin 1989c1, taken on 15-16 May 1990 confirm the presence of the broad emission features around 3.4 and 3.52 micron seen in a number of bright comets and ascribed to organic material. Both the 3.4 micron band strength and the 3.52/3.36 micron flux ratios are among the largest so far observed. The data are consistent with the relationship between band strength and water production rate that was recently derived. Excess emission at 3.28 and 3.6 micron cannot be unambiguously identified as features due to the poor signal-to-noise ratio.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Asteroids, Comets, Meteors 1991; p 211-214
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  • 5
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    Space Telescope - Eye on the universe (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The NASA Space Telescope, which is to be put into orbit by the Space Shuttle in 1985, is described with attention to the design characteristics and fabrication processes of its optics and the five scientific instruments that will be mounted at the focal plane, behind the primary mirror. The primary mirror is fabricated from Ultra Low Expansion Glass, weighed 907 kg as a blank and took three and a half years to grind and polish to a deviation of no more than 0.000025 mm from the ideal surface. The instruments carried are the Wide Field Planetary Camera, which employs CCD detectors, the Faint Object Camera, the Faint Object Spectrograph, for use at visible and UV wavelengths, the UV High Resolution Spectrograph for 1100-2300 A wavelengths, and the High Speed Photometer for the study of time-dependent brightness fluctuations.
    Keywords: ASTRONOMY
    Type: Spaceflight; 24; Dec. 198
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  • 6
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    The IRAS fast-moving object search (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The IR Astronomy Satellite (IRAS) mission has yielded an all-sky IR survey with a detailed pointing history. An analysis is being conducted which will allow an estimate to be made of the detectable population of comets and Apollo asteroids. On the basis of results obtained to date, it is expected that IRAS will detect comets having visual magnitudes lower than 17 if their motions are greater than about 1 arcmin/hour. The positional accuracy of such detections depends on the number of bands in which an object was observed, although the accuracy has so far proved unsuitable for orbit determination. There is no evidence of an undiscovered main belt asteroid population at high ecliptic latitudes.
    Keywords: ASTRONOMY
    Type: Nature (ISSN 0028-0836); 309; 315-319
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  • 7
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    The Composition of Centaur 5145 Pholus (1998)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We present a new spectrum of the Centaur object 5145 Pholus between 1.15 and 2.4 micro meters. We model this, and the previously published (0.4- to 1.0- micrometer) spectrum, using Hapke scattering theory. Seen in absorption are the 2.04- micrometer band of H2O ice and a strong band at 2.27 micrometer, interpreted as frozen methanol and/or a photolytic product of methanol having small molecular weight. The presence of small molecules is indicative of a chemically primitive surface, since heating and other processes remove the light hydrocarbons in favor of macromolecular carbon of the kind found in carbonaceous meteorites. The unusually red slope of Pholus' spectrum is matched by fine grains of a refractory organic solid (tholin). Olivine (which we model with Fo 82) also appears to be present on Pholus. We present a five-component model for the composite spectrum of all spectroscopic and photometric data available for 5145 Pholus and conclude that this is a primitive object which has not yet been substantially processed by solar heat. The properties of Pholus are those of the nucleus of a large comet that has never been active.
    Keywords: Astronomy
    Type: ICARUS: Article IS985997 (ISSN 0019-1035); Volume 135; 389-407
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  • 8
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    The Composition of Planetesimal 5145 Pholus (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We present a new spectrum of 5145 Pholus between 1.15 and 2.4 microns. We model this, and the previously published (0.4-1.0 microns) spectrum, using Hapke scattering theory. The 2.04 micron band of H2O ice is seen in absorption, as well as a strong band at 2.27 Am, interpreted as frozen methanol and/or the methanol photo product hexamethylenetetramine (HMT). The presence of small molecules is indicative of a chemically primitive surface, since heating removes the light hydrocarbons in favor of macromolecular carbon typically found in carbonaceous meteorites. The unusually red slope of Pholus' spectrum is matched by fine grains of Titan tholin, as found previously. Object 1993 HA2, which has an orbit similar to that of 5145 Pholus, is similarly red, but there are as yet no observations of absorption bands in its spectrum. We present a model for the composite spectrum of all spectroscopic and photometric data available for 5145 Pholus and conclude that this is a primitive object which has yet to be substantially processed by solar heat.
    Keywords: Astrophysics
    Type: NASA-TM-112311 , NAS 1.15:112311
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  • 9
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    Hydrogen Concentrations on C-class Asteroids from Remote Sensing (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: We present spectroscopic observations of 16 asteroids from 1.9-3.6 microns, collected from the United Kingdom Infrared Telescope (UKIRT) from 1996-2000. Of these 16 asteroids, 11 show some evidence of a 3-micron hydrated mineral absorption feature greater than 2 sigma at 2.9 microns. Using relations first recognized for carbonaceous chondrite powders by Miyamoto and Zolensky (1994) and Sato et al. (1997), we have determined the hydrogen/silicon ratio for these asteroids and calculated their equivalent water contents, assuming all the hydrogen was in water. The asteroids split into two groups, roughly defined as equivalent water contents of greater than approx. 7% (eight asteroids) and less than approx. 3 % (the remaining eight asteroids). This latter group includes some asteroids for which there is a small but statistically significant 3-micron band of non-zero depth. The G-class asteroids in the survey have higher water contents, consistent with CM chondrites. This strengthens the connection between CM chondrites and G asteroids that was proposed by Burbine (1998). We find that the 0.7-micron and 3-micron band depths are correlated for the population of target objects.
    Keywords: Astrophysics
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  • 10
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    Calculated Water Concentrations on C-Class Asteroids (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: We have spectroscopically determined the water concentrations for surfaces of 13 C-type and related asteroids using relations previously found for meteorites. We find that in general the observed asteroids have less water than the average CM meteorite. Additional information is contained in the original extended abstract.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXIII; LPI-Contrib-1109
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