Comet Halley

Nature 321, 320 - 326 (15 May 1986); doi:10.1038/321320a0

First Halley Multicolour Camera imaging results from Giotto

H. U. Keller^*, C. Arpigny^†, C. Barbieri^‡, R. M. Bonnet^§, S. Cazes, M. Coradini^¶, C. B. Cosmovici^#, W. A. Delamere^**, W. F. Huebner^††, D. W. Hughes^‡‡, C. Jamar^§§, D. Malaise^§§, H. J. Reitsema^**, H. U. Schmidt, W. K. H. Schmidt^*, P. Seige^¶¶, F. L. Whipple^## & K. Wilhelm^*

^*Max-Planck-Institut für Aeronomie, D-3411 Katlenburg-Lindau, FRG
^†Institut d'Astrophysique, and ^§§ IAL Space, Université de Liège, 4900 Liège, Belgium
^‡Istituto di Astronomia, Università di Padova, Italy
^§European Space Agency, Paris, France
Laboratoire de Physique Stellaire et Planétaire, Verrières-le-Buisson, France
^¶IAS-Reparto di Planetologia, Rome, Italy
^#Istituto Fisica Spazio Interplanetario−CNR, Frascati, Italy
^**Ball Aerospace Systems Division, Boulder, Colorado 80306, USA
^††Los Alamos National Laboratory, Los Alamos, New Mexico 875451, USA
^‡‡Physics Department, University of Sheffield, Sheffield S10 2TN, UK
Max-Planck-Institut für Astrophysik, D-8046 Garching, FRG
^¶¶Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt, D-8031 Oberpfaffenhofen, FRG
^##Smithsonian Astrophysical Observatory, Cambridge, Massachusetts 02138, USA

The first imaging results from the Halley Multicolour Camera (HMC) during the Giotto fly-by of comet Halley provide images centred on the brightest part of the inner coma which show the silhouette of a large, solid and irregularly shaped cometary nucleus and jet-like dust activity visible in reflected sunlight. A first assessment of the data yields information on the dimensions and shape of the nucleus and dust emission activity. The nucleus is at least 15 km long and 10 km wide; its geometrical albedo is very low (<4%). Only minor parts of the surface are active, most of it beirig covered by non-volatile material. Dust jets dominate the inner coma and are restricted to the sub-solar hemisphere. Preliminary interpretations of these observations are presented. The parameters of the fly-by trajectory relative to the nucleus are given.

References

1.	Whipple, F. L. Astrophys. J. 111, 375−394 (1950). | Article | ISI |
2.	Schmidt, W. K. H. et al. Eur. Space Ag. spec. Publ. 1077, 149−172 (1986).
3.	Kramm, J. R. & Keller, H. U. Adv. Electronics Electron Phys. 64A, 193−203 (1985).
4.	Keller, H. U. Eur. Space Ag. spec. Publ. 153, 57−60 (1979).
5.	Sekanina, Z. & Larson, S. M. JPL Cometary Sci. Team, Preprint No. 76 (1986).
6.	Kaneda, E. et al. Strong Breathing of the Hydrogen Coma of the Comet Halley (ISAS Res. Note 308, 1985).
7.	Grün, E. et al. Nature 321, 144−147 (1986). | ISI |
8.	Allen, C. W. Astrophysical Quantities 3rd edn, 142, 144 (Athlone, London, 1973).
9.	Hughes, D. W. Mon. Not. R. astr. Soc. 213, 103−109 (1985). | ISI |
10.	Sekanina, Z. Astr. Astrophys. 148, 299−308 (1985). | ISI | ChemPort |
11.	Bowell, E. & Lume, K. Asteroids (ed. Gehrels, T.) 132−169 (University of Arizona Press, Tucson, 1979).
12.	Divine, N. et al. JPL Cometary Sci. Team, Preprint No. 72; Space Sci. Rev. (in the press).
13.	Hellmich, R. & Keller, H. U. Icarus 47, 325−332 (1981). | Article | ISI |
14.	Cruikshank, D. P. et al. Nature 315, 122−124 (1985). | ISI |