Hostname: page-component-84b7d79bbc-5lx2p Total loading time: 0 Render date: 2024-07-26T20:08:29.742Z Has data issue: false hasContentIssue false
  • English
  • Français

The Hydrogen Clouds of Comets

Published online by Cambridge University Press:  12 April 2016

Mikio Shimizu
Mikio Shimizu*
Affiliation:
ISAS, Sagamihara Kanagawa 229, Japan

Abstract.

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

In a cometary coma, various hydrogen compounds, especially water, that are photodissociated by solar ultraviolet radiation form a gigantic hydrogen cloud with a radius of several million kilometers around the cometary nucleus. These cometary hydrogen clouds have been observed by a number of spacecraft outside the terrestrial atmosphere and in interplanetary space. For instance, the hydrogen cloud of Comet Halley was a good target for the ultraviolet photometers and spectrometers on board the International Ultraviolet Explorer (IUE), Suisei, Pioneer Venus, DE-1, and sounding rockets. Hydrogen cloud activity could be used as a good measure of cometary activity, but some problems remain to be explored in the future.

Type
Section V: The Cometary Coma
Information
International Astronomical Union Colloquium , Volume 116 , Issue 2: Comets in the Post-Halley Era , 1991 , pp. 897 - 905
Copyright
Copyright © Kluwer 1991

References

Brozowski, J., et al. (1978). “Precision Estimates of the Predissociation Rates of the OH A State (2Σ+),” Phys. Scripta, 17, 507–511.Google Scholar
Carruthers, G.R., et al. (1974). “Lyman Alpha Imaginary of Comet Kohoutek,” Icarus, 23, 526–537.Google Scholar
Code, A.D., and Savage, D. (1972). “OAO: Review of Scientific Results,” Science, 177, 213–221.Google Scholar
Combi, M.R., and Delsemme, A.H. (1980). “Neutral Cometary Atmosphere I. An Average Random Walk Model for Photodissociation in Comets,” Ap. J., 237, 633–640.Google Scholar
Combi, M.R., and Smith, W.H. (1988a). “Monte Carlo Particle-Trajectory Models for Neutral Cometary Gases I. Models and Equations,” Ap. J., 327, 1026–1043.Google Scholar
Combi, M.R., and Smith, W.H. (1988b). “Monte Carlo Particle-Trajectory Models for Neutral Cometary Gases II. The Spectral Morphology of the Lyman Alpha Coma,” Ap. J., 327, 1045–1059.Google Scholar
Divine, N., et al. (1986). “The Comet Halley Dust and Gas Environments,” Space Sci. Rev., 3, 1–104.CrossRefGoogle Scholar
Drake, J.F., et al. (1976). “Lyman Alpha Observations of Comet Kohoutek,” Ap. J., 209, 302–311.Google Scholar
Feldman, P.D. (1982). “Ultraviolet Spectroscopy of Comae,” in Wilkening, L.L. (ed.), Comets, The University of Arizona Press, Tucson, pp. 461–479.Google Scholar
Feldman, P.D., et al. (1980). “IUE Observation of the UV Spectrum of Comet Bradfield,” Nature, 286, 132–135.Google Scholar
Feldman, P.D., et al. (1987). “IUE Observation of P/Halley,” Astron. Astrophys., 187, 325–328.Google Scholar
Festou, M.C. (1981). “The Density Distribution of Neutral Compounds in Cometary Atmospheres I. Models and Equations,” Astron. Astrophys., 95, 69–79.Google Scholar
Festou, M.C. (1986). “Comets,” ESA SP-263, pp. 3–9.Google Scholar
Festou, M.C. (1988). “Variation of the Gaseous Output of the Nucleus of Comet P/Halley,” in Mason, J. and Moore, P. (eds.), Comet Halley Worldwide Investigations, Results, and Interpretation, in press.Google Scholar
Festou, M.C., and Feldman, P.D. (1987). “Comets,” in Kondo, Y. (ed.), Scientific Accomplishments of the IUE, D. Reidel Publ. Comp., Dordrecht, pp. 101–118.Google Scholar
Festou, M., et al. (1979). “Lyman Alpha Observations of Comet Kobayashi-Berger-Milon (1975 IX) with Copernicus,” Ap. J., 232, 318–328.Google Scholar
Festou, M.C., et al. (1983). “IUE Observation of Comet P/Crommelin,” Astron. Astrophys., 152, 170–172.Google Scholar
Festou, M.C., et al. (1983). “Lyman Alpha Observations of Comet West and P/d’Arrest with Copernicus,” Ap. J., 265, 925–932.Google Scholar
Kaneda, E., et al. (1986a). “Activity of Comet Halley Observed in the Ultraviolet,” Geophys. Res. Let., 13, 833–836.Google Scholar
Kaneda, E., et al. (1986b). “Strong Breathing of the Hydrogen Coma of Comet Halley,” Nature, 320, 140–141.CrossRefGoogle Scholar
Kaneda, E., et al. (1986c). “Observation of Comet Halley by the Ultraviolet Imager of Suisei,” Nature, 321, 297–299.Google Scholar
Keller, H.U. (1973a). “Lyman Alpha Radiation in the Hydrogen Atmospheres of Comets: A Model with Multiple Scattering,” Astron. Astrophys., 23, 269–280.Google Scholar
Keller, H.U. (1973b). “Hydrogen Production Rates of Comet Bennett in the First Half of April, 1970,” Astron. Astrophys., 27, 51–57.Google Scholar
Keller, H.U. (1974). “The Scale Length of OH and the Production Rates of H and OH in Comet Bennett,” Astron. Astrophys., 34, 187–196.Google Scholar
Keller, H.U. (1975). “A Cometary Hydrogen Model: Comparison with OGO-5 Measurements of Comet Bennett,” Astron. Astrophys., 39, 7–19.Google Scholar
Keller, H.U. (1976). “The Interpretations of Ultraviolet Observations of Comets,” Space Sci. Rev., 18, 641–684.Google Scholar
Keller, H.U., and Lillie, C.F. (1978). “Hydrogen and Hydroxyl Production Rates of Comet Tago-Sato-Kosaka,” Astron. Astrophys., 62, 143–147.Google Scholar
Keller, H.U., and Meier, R.R. (1976). “A Cometary Hydrogen Model for Arbitrary Observational Geometry,” Astron. Astrophys., 52, 273–281.Google Scholar
Keller, H.U., and Meier, R.R. (1980). “On the Lyman Alpha Isophotes of Comet West,” Astron. Astrophys., 81, 210–214.Google Scholar
Keller, H.U., and Thomas, G.E. (1976). “A High Velocity Component of Atomic Hydrogen in Comet Bennett,” Proc. IAU Collog. No. 25, 316–321.Google Scholar
Keller, H.U., et al. (1975). “High Resolution Lyman Alpha Observations of Comet Kohoutek Near Perihelion,” Astron. Astrophys., 38, 413–416.Google Scholar
Kitamura, Y. (1986). “Axisymmetric Dusty Gas Jet in the Inner Coma of a Comet,” Icarus, 66, 245–257.Google Scholar
Kitamura, Y., et al. (1985). “A Model for the Hydrogen Coma of a Comet,” Icarus, 61, 278–295.Google Scholar
Larson, S.M., and Sekanina, Z. (1985). “Coma Morphology and Dust-Emission Pattern of Periodic Comet Halley. III. Additional High Resolution Images Taken in 1910,” Astron. J., 90, 823–826.Google Scholar
McCoy, R.P., et al. (1986). “Far-Ultraviolet Spectral Images of Comet Halley from Sounding Rockets,” Nature, 324, 439–441.Google Scholar
Meier, R.R., et al. (1976). “Hydrogen Production Rate from Lyman Alpha Images of Comet Kohoutek,” Astron. Astrophys., 52, 283–290.Google Scholar
Millis, R.L., and Schleider, D.G. (1986). “Rotational Period of Comet Halley,” Nature, 324, 646–649.Google Scholar
Opal, C.B., and Carruthers, G.R. (1975). “Lyman Alpha Observation of Comet West,” Icarus, 31, 503–509.Google Scholar
Opal, C.B., et al. (1974). “Comet Kohoutek: Ultraviolet Images and Spectrograms,” Science, 185, 702–705.Google Scholar
Shimizu, M. (1986). “Hydrogen Coma of Comet Halley,” Adv. Space Res., 5, 73–81.Google Scholar
Shimizu, M. (1987). “Halley’s Environments Observed by the Japanese Suisei Spacecraft,” ESA SP-278, 229–232.Google Scholar
Stewart, A.I.F. (1987). “Pioneer Venus Measurement of H, O, and C Production in Comet P/Halley Near Perihelion,” Astron. Astrophys., 187, 369–374.Google Scholar
Wallis, M.K., and Carey, W.C. (1985). “Observation of Comet Crommelin-V: Anomalous Hydrogen Source,” Month. Nat. R. Astr. Soc, 217, 673–678.Google Scholar
Weaver, H.A., et al. (1981a). “IUE Observations of Faint Comets,” Icarus, 47, 449–463.Google Scholar
Weaver, H.A., et al. (1981b). “Water Production Models for Comet Bradfield,” Ap. J., 251, 809–815.Google Scholar
Weissman, P.R. (1987). “Post-Perihelion Brightening of Comet P/Halley: Springtime for Halley,” Astron. Astrophys., 187, 873–878.Google Scholar
Weissman, P.R., and Kieffer, H.H. (1979). “Thermal Modeling of Cometary Nuclei,” Icarus, 47, 302–311.Google Scholar
West, R.M., and Pederson, H. (1984). “Variability of P/Halley,” Astron. Astrophys., 138, L9–L10.Google Scholar