No CrossRef data available.
Article contents
Physical Aging in Comets
Published online by Cambridge University Press: 12 April 2016
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.
Recent evidence suggests that comets formed at low temperatures (≤ 25 K) and that, while the interiors have not been considerably altered since formation, the outer layers have undergone substantial modification. Comets exhibit a wide range of physical characteristics, some of which may be attributed to systematic physical differences between comets making their first close approach to the Sun from the Oort cloud (new comets) and those having made many approaches (old comets). These differences may reflect either primordial differences between two populations or the differences may be a manifestation of aging processes. There are many processes that might be responsible for causing aging in comets. These include: (i) radiation damage in the upper layers of the nucleus during the long residences in the Oort cloud, (ii) processing from heating and collisions within the Oort cloud, (iii) loss of highly volatile species from the nucleus on the first passage through the inner Solar System, (iv) buildup of a dusty mantle, which can eventually prohibit further sublimation, and (v) a change in the porosity, and hence the thermal properties of the nucleus. Although Oort’s (1950) original work on the comet cloud required that new comets fade after their first close passage, past searches for evidence of aging in comets have produced conflicting results, partly due to a lack of systematic data sets. An understanding of the evolutionary processes of comet nuclei that give rise to compositional or physical differences between ‘fresh’ Oort cloud comets and thermally processed periodic comets will improve our knowledge of the possibly primordial comet composition and therefore conditions in the early Solar System. Recent observations suggest that there are distinct differences between the two groups with respect to intrinsic brightness and rate of change of activity as a function of distance.
- Type
- Section III: Comets, Origins, and Evolution
- Information
- International Astronomical Union Colloquium , Volume 116 , Issue 1: Comets in the Post-Halley Era , 1989 , pp. 629 - 669
- Copyright
- Copyright © Kluwer 1991
References
A’Hearn, M.F., and P.D., Feldman (1984). “S2: A Clue to the Origin of Cometary Ice?”, in Ices in the Solar System, eds. Klinger, J., Benest, D., Dollfus, A., and Smoluchowski, R., NATO Adv. Sci. Inst. Series C., Vol. 156, D. Reidel Pub. Co., Dordrecht, pp. 463–471.Google Scholar
A’Hearn, M.F., Feldman, P.D., and Schleicher, D.G. (1983). “The Discovery of S2 in Comet IRAS-Araki-Alcock,” Astrophys. J. Lett. 274, L99–L103.Google Scholar
A’Hearn, M.F., Millis, R.L., and Birch, P.V. (1979). “Gas and Dust in Some Recent Periodic Comets,” Astron. J.
84, 570–579.CrossRefGoogle Scholar
Arpigny, C., Dossin, F., Manfroid, J., Magain, P. and Haefner, R. (1988). “Pre- and Post Perihelion Spectrographic and Photometric Observations of Comet Wilson (19861),” Messenger
51
27–31.Google Scholar
Bailey, M.E. (1985). “The Problem of the 1/a-Distribution and Cometary Fading,” in Dynamics of Comets: Their Origin and Evolution, IAU Colloquium No. 83, eds. Carusi, A., and Valsecchi, G.B.
D. Reidel Pub. Co., Dordrecht, pp. 311–317.Google Scholar
Bar-Nun, A., and Prialnik, D. (1989). “Formation of Comets—Laboratory Studies and Modelling,” in Asteroids, Comets, Meteors III, Abstracts, Uppsala Astronomical Observatory Report No. 48, Uppsala, #11.Google Scholar
Barnard, E.E. (1890). “Comets 1889 I and II, and Some Suggestions as to the Possibility of Seeing the Short-Period Comets at Aphelion,” Astron. J.
10, 67–68.CrossRefGoogle Scholar
Belton, M.J.S. (1965). “Some Characteristics of Type II Comet Tails and the Problem of the Distant Comets,” Astron. J.
70, 451–465.CrossRefGoogle Scholar
Brin, G.D., and Mendis, D.A. (1979). “Dust Release and Mantle Development in Comets,” Astrophys. J.
229, 402–408.Google Scholar
Cochran, A.L. (1987). “Another Look at Abundance Correlations Among Comets,” Astron. J.
93, 231–238.Google Scholar
Cochran, A.L., Barker, E.S., and Cochran, W.D. (1980). “Spectrophotometric Observations of P/Schwassmann-Wachmann 1 During Outburst,” Astron. J.
85, 474–477.Google Scholar
Cochran, A.L., Green, J.R., and Barker, E.S. (1989a). “Are Low Activity Comets Intrinsically Different From More Active Comets?”, Icarus
79, 125–144.Google Scholar
Cremonese, G., and M., Fulle (1989). “Photometric Analysis of the Dust Tail of Comet Wilson 1987VII,” poster paper presented at the “Comets in the Post-Halley Era” meeting, Bamberg, FRG.Google Scholar
d’Hendecourt, L.B, Allamandola, L.J., Grim, R.J.A., and Greenberg, J.M. (1986). “Time-Dependent Chemistry in Dense Molecular Clouds. II. Ultraviolet Photoprocessing and Infrared Spectroscopy of Grain Mantles,” Astron. Astrophys.
158, 119–134.Google Scholar
Degewij, J., and Tedesco, E.F. (1982). “Do Comets Evolve into Asteroids? Evidence From Physical Studies,” in Comets, ed. Wilkening, L.L., University of Arizona Press, Tucson, Arizona, pp. 665–695.Google Scholar
Delsemme, A.H. (1975). “Physical Interpretation of the Brightness Variation of Comet Kohoutek,” in Comet Kohoutek, ed. Gary, G.A., Scientific and Technical Information Office, NASA, Washington, pp. 195–203.Google Scholar
Delsemme, A.H. (1982). “Chemical Composition of Cometary Nuclei,” in Comets, ed. Wilkening, L.L., University of Arizona Press, Tucson, Arizona, pp. 85–130.Google Scholar
Delsemme, A.H. (1985). “The Sublimation Temperature of the Cometary Nucleus: Observational Evidence for H2O Snows,” in Ices in the Solar System, eds. Klinger, J., Benest, D., Dollfus, A., and Smoluchowski, R., NATO Adv. Sci. Inst. Series C., Vol. 156, D. Reidel Pub. Co., Dordrecht, pp. 367–387.Google Scholar
Delsemme, A.H., and Swings, P. (1952). “Hydrates de Gaz Dans les Noyaux Comètaires et les Grains Interstellaires,” Ann. d’ Astrophys.
15, 1–6.Google Scholar
Divine, N., and Newbum, R.L. (1987). “Modelling Halley Before and After the Encounters,” Astron. Astrophys.
187, 867–872.Google Scholar
Donn, B. (1976). “The Nucleus: Panel Discussion,” in The Study of Comets, ed. Donn, B., Mumma, M., Jackson, W., A’Hearn, M., and Harrington, R., NASA SP-393, Part 2, Washington, D.C. pp. 611–621.Google Scholar
Donn, B. (1977). “A Comparison of the Composition of New and Evolved Comets,” in Comets, Asteroids, Meteorites: Interrelations, Evolution and Origins, ed. Delsemme, A.H., University of Toledo, Toledo, Ohio, pp. 15–23.Google Scholar
Donn, B., and Urey, H.C. (1955). “On the Mechanism of Comet Outbursts and the Chemical Composition of Comets,” Astrophys. J.
123, 339–342.Google Scholar
Dossin, F.V. (1966). “Emission Spectrum of a Comet, at Large Heliocentric Distance,” Astron. J.
71, 853–854.Google Scholar
Duncan, M., Quinn, T., and Tremarne, S. (1988). “The Origin of Short-Period Comets,” Astrophys. J.
328, L69–L73.Google Scholar
Everhart, E., and Marsden, B.G. (1983). “New Original and Future Cometary Orbits,” Astron. J.
88, 135–137.Google Scholar
Everhart, E., and Marsden, B.G. (1987). “Original and Future Cometary Orbits. III,,” Astron. J.
93, 753–754.Google Scholar
Fanale, F.P., and J.R., Salvail (1984). “An Idealized Short-Period Comet Model: Surface Insolation, H2O Flux, Dust Flux and Mantle Evolution,” Icarus
60, 476–511.Google Scholar
Fanale, F.P., and Salvail, J.R. (1987). “The Loss and Depth of CO2 Ice in Comet Nuclei,” Icarus
72, 535–554.Google Scholar
Fanale, F.P., and Salvail, J.R. (1990). “The Influence of CO Ice on the Activity and Near Surface Differentiation of Comet Nuclei,” Icarus
84, 403–413.CrossRefGoogle Scholar
Feldman, P.D., A’Hearn, M.F., Festou, M.C., McFadden, L.A., Weaver, H.A. and Woods, T.N. (1986). “Is CO2 Responsible for the Outbursts of Comet Halley?”, Nature
324, 433–436.Google Scholar
Feldman, P.D., and Brune, W.H. (1976). “Carbon Production in Comet West 1975n,” Astrophys. J.
209, L45–L48.Google Scholar
Feldman, P.D, Festou, M.C., A’Hearn, M.F., Arpigny, C., Butterworth, P.S., Cosmovici, C.B., Danks, A.C., Gilmozzi, R., Jackson, W.M., McFadden, L.A., Patriarchi, P., Schleicher, D.G., Tozzi, G.P., Wallis, M.K., Weaver, H.A., and Woods, T.N. (1987). “IUE Observations of Comet P/Halley: Evolution of the Ultraviolet Spectrum Between September 1985 and July 1986,” Astron. Astrophys.
187, 325–328.Google Scholar
Feldman, P.D., Takacs, P.Z., and Fastie, W.G. (1974). “Rocket Ultraviolet Spectrophotometry of Comet Kohoutek (1973f),” Science
185, 705–707.CrossRefGoogle ScholarPubMed
Festou, M.C., Lecacheux, J., Kohl, J.L.
Encrenaz, T., Baudrand, J., Combes, M., Despiau, R., Laques, P., Le fèvre, O., Lemonnier, J.P., Lelièvre, G., Mathez, G., Pierre, M., and Vidal, J.L. (1986). “Photometry and Activity of the Nucleus of P/Halley at Heliocentric Distances Larger than 4.6 AU, Pre-Perihelion,” Astron. Astrophys.
169, 336–344.Google Scholar
Green, D.W.E., and Morris, C. S. (1987). “The Visual Brightness Behavior of P/Halley During 1981-1987,” Astron. Astrophys.
187, 560–568.Google Scholar
Greenberg, J.M. (1977). “From Dust to Comets,” in Comets, Asteroids, Meteorites: Interrelations, Evolution and Origins, ed. Delsemme, A.H., University of Toledo, Toledo, Ohio, pp. 491–497.Google Scholar
Greenberg, J.M. (1982). “What Are Comets Made of? A Model Based on Interstellar Dust,” in Comets, ed. Wilkening, L.L., University of Arizona Press, Tucson, Arizona, pp. 131–163.Google Scholar
Greenberg, J.M. (1987). “Comet Halley: A Carrier of Interstellar Dust Chemical Evolution,” Adv. Space Res.
7, No. 5, 33–44.CrossRefGoogle Scholar
Greenberg, J.M., Grim, R., and van IJzendoorn, L. (1986). “Interstellar S2 in Comets,” in Asteroids, Comets, and Meteors, II, eds. Lagerkvist, C.-I., Lindblad, B.A., Lundstedt, H. and Rickman, H., Uppsala, pp. 225–227.Google Scholar
Greenstein, J.L. (1962). “The Spectram of Comet Humason (1961e),” Astrophys. J.
136, 688–690.Google Scholar
Grim, R.J.A., and Greenberg, J.M. (1987). “Photoprocessing of H2S in Interstellar Grain Mantles as an Explanation for S2 in Comets,” Astron. Astrophys.
181, 155–168.Google Scholar
Hanner, M.S., and Newburn, R.L. (1989). “Infrared Photometry of Comet Wilson (19861) at Two Epochs,” Astron. J.
97, 254–261.CrossRefGoogle Scholar
Hartmann, W.K., Tholen, D.J., and Cruikshank, D.P. (1987). “The Relationship of Active Comets, ‘Extinct’ Comets, and Dark Asteroids,” Icarus
69, 33–50.Google Scholar
Hartmann, W.K., Tholen, D.J., Meech, K.J., and Cruikshank, D.P. (1989). “2060 Chiron: Colorimetry and Cometary Behavior,” Icarus
83, 1–15.CrossRefGoogle Scholar
Horanyi, M., Gombosi, T.I., Cravens, T.E., Korosmezey, A., Kecskemety, K., Nagy, A.F., and Szego, K. (1984). “The Friable Sponge Model of a Cometary Nucleus,” Astrophys. J.
278, 449–455.Google Scholar
Houpis, H.L.F., and Mendis, D.A. (1981). “Dust Emission From Comets at Large Heliocentric Distances,” Moon and Planets
25, 397–412.Google Scholar
Houpis, H.L.F., Ip, W.-H., and Mendis, D.A. (1985). “The Chemical Differentiation of the Cometary Nucleus: The Process and its Consequences,” Astrophys. J.
295, 654–667.Google Scholar
Hughes, D.W. (1975). “Cometary Outbursts, A Brief Survey,” Quar. J. R. Astr. Soc.
16, 410–427.Google Scholar
Jewitt, D., and Meech, K.J. (1986). “Cometary Grain Scattering Versus Wavelength or ’What Color is Comet Dust?’,” Astrophys. J.
310, 937–952.Google Scholar
Jewitt, D., and Meech, K.J. (1988). “The Absence of a Color-Distance Trend in Comets,” Astron. J.
96, 1723–1730.Google Scholar
Johnson, R.E., Cooper, J.F., Lanzerotti, L.J., and Strazzulla, G. (1987). “Radiation Formation of a Non-Volatile Comet Crust,” Astron. Astrophys.
187, 889–892.Google Scholar
Keller, H.U., Delamere, W.A., Huebner, W.F., Reitsema, H.J., Schmidt, H.U., Whipple, F.L., Wilhelm, K., Curdt, W., Kramm, R., Thomas, N., Arpigny, C., Barbieri, C., Bonnet, R.M., Cazes, S., Coradini, M., Cosmovici, C.B., Hughes, D.W., Jamar, C., Malaise, D., Schmidt, K., Schmidt, W.K.H., and Seige, P. (1987). “Comet P/Halley’s Nucleus and Its Activity,” Astron. Astrophys.
187, 807–823.Google Scholar
Klinger, J. (1980). “Influence of a Phase Transition of Ice on the Heat and Mass Balance of Comets,” Science
209, 271–272.Google Scholar
Klinger, J. (1981). “Some Consequences of a Phase Transition of Water Ice on the Heat Balance of Cometary Nuclei,” Icarus
47, 320–324.Google Scholar
Krankowsky, D.P.
Lämmerzahl, I.
Herrwerth, J.
Woweries, P.
Eberhardt, U.
U., Dolder
Herrmann, W.
Schulte, J.J.
Berthelier, J.M.
Illiano R.R., Hodges, and Hoffman, J.H. (1986). “ In Situ Gas and Ion Measurements at Comet Halley,” Nature
321, 326–329.Google Scholar
Kresák, L. (1977). “An Alternate Interpretation of the Oort Cloud of Comets?,”in Comets, Asteroids, Meteorites: Interrelations, Evolution and Origins, ed. Delsemme, A.H., University of Toledo, Toledo, Ohio, pp. 93–97.Google Scholar
Kresák, L. (1979). “Dynamical Interrelations Among Comets and Asteroids,” in Asteroids, ed. Gehreis, T., Univ. of Arizona Press, Tucson, AZ, 289–309.Google Scholar
Marsden, B.G. (1970). “On the Relationship Between Comets and Minor Planets,” Astron. J.
75, 206–217.CrossRefGoogle Scholar
Marsden, B.G. (1986). Catalog of Cometary Orbits, IAU Central Bureau for Astronomical Telegrams, SAO, Cambridge, MA.Google Scholar
Marsden, B.G., and Sekanina, Z. (1973). “On the Distribution of Original’ Orbits of Comets of Large Perihelion Distance,” Astron. J.
78, 1118–1124.Google Scholar
Marsden, B.G., Sekanina, Z., and Everhart, E. (1978). “New Osculating Orbits for 110 Comets and Analysis of Original Orbits for 200 Comets,” Astron. J.
83, 64–71.Google Scholar
Marsden, B.G., Sekanina, Z., and Yeomans, D.K. (1973). “Comets and Nongravitational Forces. V.,” Astron. J.
78, 211–225.Google Scholar
Meech, K.J. (1988b). “Distant, Active Comets Observable From the Southern Hemisphere,” in Progress and Opportunities in Southern Hemisphere Optical Astronomy—Proceedings of the CTIO 25th Anniversary Celebration, eds. Blanco, V.M. and Phillips, M.M., A.S.p. Conf. Series 1, 335–341.Google Scholar
Meech, K.J., and Belton, M.J.S. (1990). “The Atmosphere of 2060 Chiron,” Astron. J.,submitted.Google Scholar
Meech, K.J., and Jewitt, D.C. (1987). “Observations of Comet Bowell at Record Heliocentric Distance,” Nature
328, 506–509.Google Scholar
Meech, K.J., Jewitt, D., and Ricker, G.R. (1986). “Early Photometry of Comet P/Halley: Development of the Coma,” Icarus
66, 561–574.Google Scholar
Mendis, D.A., and Brin, G.D. (1977). “Monochromatic Brightness Variations of Comets. II. Core-Mantle Model,” Moon
17, 359–372.Google Scholar
Mendis, D.A., and Brin, G.D. (1978). “On the Monochromatic Brightness Variations of Comets,” Moon and Planets
18, 77–89.Google Scholar
Moore, M.H., Donn, B., Khanna, R., and A’Hearn, M.F. (1983). “Studies of Proton-Irradiated Cometary-Type Ice Mixtures,” Icarus
54, 388–405.Google Scholar
Mumma, M.J. (1989). “Probing Solar System Objects at Infrared Wavelengths,” Infrared Physics
29, 167–174.Google Scholar
Mumma, M.J., Blass, W.E., Weaver, H.A., and Larson, H.P. (1988). “Measurements of the Ortho-Para Ratio and Nuclear Spin Temperature of Water Vapor in Comets Halley and Wilson (1986l) and Implications for Their Origin and Evolution,” Bull. Amer. Astron. Soc.
20, 826
Google Scholar
Mumma, M.J., Blass, W.E., Weaver, H.A., and Larson, H.P. (1990). “Measurements of the Ortho-Para Ratio and Nuclear Spin Temperature of Water Vapor in Comets Halley and Wilson (1986l) and Implications for Their Origin and Evolution,” STSI Conf. on Origins and Evolution of Planetary Systems, in press.Google Scholar
Mumma, M.J., Weaver, H.A., and Larson, H.P. (1987). “The Ortho-Para Ratio of Water Vapor in Comet P/Halley,” Astron. Astrophys.
187, 419–424.Google Scholar
Mumma, M.J., Weaver, H.A., Larson, H.P., Davis, D.S., and Williams, M. (1986). “Detection of Water Vapor in Halley’s Comet,” Science
232, 1523–1528.Google Scholar
Newburn, R.L., and Spinrad, H. (1989). “Spectrophotometry of 25 Comets: Post-Halley Update for 17 Comets Plus New Observations for Eight Additional Comets,” Astron. J.
97, 552–569.Google Scholar
Oikawa, S., and Everhart, E. (1979). “Past and Future Orbit of 1977 UB, Object Chiron,” Astron. J.
84, 134–139.Google Scholar
Oort, J.H. (1950). “The Structure of the Cloud of Comets Surrounding the Solar System, and a Hypothesis Concerning its Origin,” Bull. Astron. Inst. Neth. Vol. 11, No. 408, 91–110.Google Scholar
Oort, J.H., and Schmidt, M. (1951). “Differences Between New and Old Comets,” Bull. Astron. Inst. Neth. Vol. 11, No. 419, 259–269.Google Scholar
Palmer, P., de Pater, I., and Snyder, L.E. (1989). “VLA Observations of the OH Emission From Comet Wilson (1986l): The Value of High Resolution in Both Spatial and Velocity Coordinates,” Astron. J.
97, 1791–1797.Google Scholar
Patashnick, H., Rupprecht, G., and Schuerman, D.W. (1974). “Energy Source for Comet Outbursts,” Nature
250, 313–314.Google Scholar
Prialnik, D., and Bar-Nun, A. (1987). “On The Evolution and Activity of Cometary Nuclei,” Astrophys. J.
313, 893–905.Google Scholar
Rickman, H. (1985). “Interrelations Between Comes and Asteroids,” in Dynamics of Comets: Their Origin and Evolution, IAU Colloquium No. 83, eds. Carusi, A., and Valsecchi, G.B., D. Reidel Pub. Co., Dordrecht, pp. 149–172.Google Scholar
Roemer, E. (1962). “Activity in Comets at Large Heliocentric Distance,” Pub. Astron. Soc. Pacific
74, 351–365.Google Scholar
Roettger, E.E., and Feldman, P.D. (1990). “Comet Austin (1989c1),” IAU Circ. No. 4934.Google Scholar
Roettger, E.E., Feldman, P.D., A’Hearn, M.F., Festou, M.C., McFadden, L.A., and Gilmozzi, R. (1989). “IUE Observations of the Evolution of Comet Wilson (1986l): Comparison With P/Halley,” Icarus
80, 303–314.Google Scholar
Sandford, S.A., and Allamandola, L.J. (1988). “The Condensation and Vaporization Behavior of H2O:CO Ices and Implications for Interstellar Grains and Cometary Activity,” Icarus
76, 201–224.CrossRefGoogle Scholar
Schleicher, D.G., Osip, D.J., and Birch, P.V. (1990). “Comet Austin (1989c1),” IAU Circ. No. 4983.Google Scholar
Sekanina, Z. (1973). “Existence of Icy Comet Tails at Large Distance From the Sun,”Astrophys. Lett.
14, 175–180.Google Scholar
Sekanina, Z. (1975). “A Study of the Icy Tails of the Distant Comets,” Icarus
25, 218–238.Google Scholar
Sekanina, Z. (1979). “Fan-Shaped Coma, Orientation of Rotation Axis, and Surface Structure of a Cometary Nucleus I. Test of a Model on Four Comets,” Icarus
37, 420–442.Google Scholar
Sekanina, Z. (1982a). “The Problem of Split Comets in Review,” in Comets, ed. Wilkening, L.L., University of Arizona Press, Tucson, Arizona, pp. 251–287.Google Scholar
Sekanina, Z. (1982b). “Comet Bowell (1980b): An Active-Looking Dormant Object?”, Astron. J.
87, 161–169.CrossRefGoogle Scholar
Smoluchowski, R. (1981). “Heat Content and Evolution of Cometary Nuclei,” Icarus
47, 312–319.Google Scholar
Smoluchowski, R. (1985). “Amorphous and Porous Ices in Cometary Nuclei,” in Ices in the Solar System, eds. Klinger, J., Benest, D., Dollfus, A., and Smoluchowski, R., NATO Adv. Sci. Inst. Series C., Vol. 156, D. Reidel Pub. Co., Dordrecht, pp. 397–406.Google Scholar
Smoluchowski, R. (1986). “Brightness Curve and Porosity of Cometary Nuclei,” in Asteroids, Comets, and Meteors, II, eds. Lagerkvist, C.-I., Lindblad, B.A., Lundstedt, H. and Rickman, H., Uppsala, pp. 305–315.Google Scholar
Smoluchowski, R. (1989). “Properties of Mantles on Cometary Nuclei,” Astron. J.
97, 241–245.Google Scholar
Stern, S.A. (1989a). “ISM-Induced Erosion and Gas-Dynamical Drag in the Oort Cloud,” Icarus
84, 447–466.CrossRefGoogle Scholar
Stern, S.A. (1989b). “Implications of Volatile Release From Object 2060 Chiron,” Pub. Astr. Soc. Pac.
101, 126–132.Google Scholar
Stern, S.A., and Shull, J.M. (1988). “The Influence of Supernovae and Passing Stars on Comets in the Oort Cloud,” Nature
332, 407–411.Google Scholar
Svoren, J. (1983). “Photometric Observations of Long Period Comets at Large Heliocentric Distances in the Years 1861 to 1925,” Contributions of the Astron. Obs. Skalnaté Pleso
11, 95–123.Google Scholar
Svoren, J. (1984). “Photometric Observations of Long Period Comets at Large Heliocentric Distances in the Years 1927 to 1955,” Contributions of the Astron. Obs. Skalnaté Pleso
12, 7–44.Google Scholar
Svoren, J. (1985). “Photometric Observations of Long Period Comets at Large Heliocentric Distances in the Years 1956-1976,” Contributions of the Astron. Obs.Skalnaté Pleso
13, 93–125.Google Scholar
Svoren, J. (1986). “Variations of Photometric Exponents of Long-Period Comets at Large Heliocentric Distances,” in Asteroids, Comets, and Meteors, II, eds. Lagerkvist, C.-I., Lindblad, B.A., Lundstedt, H. and Rickman, H., Uppsala, pp. 323–326.Google Scholar
Tholen, D.J., Hartmann, W.K., and Cruikshank, D.P. (1988). “2060 Chiron,” IAU Circ. No. 4554.Google Scholar
Tokunaga, A.T., Golisch, W.F., Griep, D.M., Kaminski, C.D., and Hanner, M.S. (1988). “The NASA Infrared Telescope Facility Comet Halley Monitoring Program II. Postperihelion Results,” Astron. J.
96, 1971-1976.Google Scholar
Weissman, P.R. (1979). “Nongravitational Perturbations of Long-Period Comets,” Astron. J.
84, 580–584.Google Scholar
Weissman, P.R. (1982). “Dynamical History of the Oort Cloud,” in Comets, ed. Wilkening, L.L., University of Arizona Press, Tucson, Arizona, pp. 637–658.CrossRefGoogle Scholar
Weissman, P.R. (1986). “The Oort Cloud and the Galaxy: Dynamical Interactions,” in The Galaxy and the Solar System, eds. Smoluchowski, R., Bahcall, J.N., and Matthews, M.S., University of Arizona Press, Tucson, Arizona, pp. 204–237.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 Stern, S.A. (1989). “Physical Processing of Cometary Nuclei,” submitted to Proc. of the Workshop on Analysis of Returned Comet Nucleus Samples, Milpitas, CA.
Google Scholar
Weissman, P.R., A’Hearn, M.F., McFadden, L.A., and Rickman, H. (1989). “Evolution of Comets Into Asteroids,” in ?Asteroids II, eds. Binzel, R., Gehrels, T., and Matthews, M.S., University of Arizona Press, Tucson, Arizona, pp. 880–920.Google Scholar
West, R.M. (1990). “Post-Perihelion Observations of Comet Halley. II (R = 10.1 AU),” Astron. Astrophys.
228, 531–538.Google Scholar
West, R.M., and Jørgensen, H.E. (1990). “Post Perihelion Observations of Comet Halley at R = 8.5 AU,” Astron. Astrophys.
218, 307–316.Google Scholar
Whipple, F.L. (1950). “A Comet Model. I. The Acceleration of Comet Encke,” Astrophys. J.
111, 375–394.Google Scholar
Whipple, F.L. (1977). “The Constitution of Cometary Nuclei,” in Comets, Asteroids, Meteorites: Interrelations, Evolution and Origins, ed. Delsemme, A.H., University of Toledo, Toledo, Ohio, pp. 25–35.Google Scholar
Whipple, F.L. (1978). “Cometary Brightness Variation and Nucleus Structure,” Moon and Planets
18, 343–359.Google Scholar
Whipple, F.L. (1989). “Comets in the Space Age,” CFA Preprint Series No. 2707, Astrophys. J., submitted.Google Scholar
Woods, T.N., Feldman, P.D., Dymond, K.F., and Sahnow, D.J. (1986). “Rocket Ultraviolet Spectroscopy of Comet Halley and Abundance of Carbon Monoxide and Carbon,” Nature
324, 426–438.Google Scholar
Wyckoff, S.
Wagner, M., Wehinger, P.A., Schleicher, D.G., and Festou, M.C. (1985). “Onset of Sublimation in Comet P/Halley (1982i),” Nature
316, 241–242.Google Scholar
You have
Access