Ground-based near-infrared imaging of Comet P/Halley 1986 III

Charles E. Woodward, Mark A. Shure, William J. Forrest, T. J. Jones, R. D. Gehrz, Tetsuya Nagata, Alan T. Tokunaga

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We present an analysis of 1-to 5-μm, near-infrared broadband images of Comet P/Halley 1986 III covering a 104-km square region of the inner coma obtained on three consecutive nights in 1986 March during post-perihelion passage. In all images, the coma is extended in the sunward direction and appears distinctly non-spherical, similar to morphology in the 10-μm made by Hayward et al. (1987) 3.0 days later during the Giotto encounter. Marked variation in the coma's overall structure and brightness also was apparent, including the presence of a jet feature which we associate with a short-term outburst of material from the comet nucleus. The observed coma surface brightness dependence upon nucleocentric distance (r) at all wavelengths in both the comet dust tail and in the jet deviates from the dependence predicted by the "steady state" model for comet nucleus ablation, with the radial decrease in surface brightness being slower than r-1 on the jet side of the nucleus and faster that r-1 on the tail side. The near-infrared colors of the coma are not constant as a function of nucleocentric distance, suggesting that the grain properties are not uniform across the coma. Based on an elementary dynamical analysis of the trajectories of dust particles ablated from the nucleus we argue that these observations may be consistent with the hypothesis that particles emitted in jets fragments in the outflow on time scales of a few hours.

Original languageEnglish (US)
Pages (from-to)651-662
Number of pages12
Issue number2
StatePublished - Dec 1996

Bibliographical note

Funding Information:
We thank the IRTF staff for helping to make this a useful observing run. We thank Nicholas Raines for assistance in reducing data and the referees whose comments improved the manuscript. The infrared array in the University of Rochester camera was on loan from the Santa Barbara Research Center. This research was supported by grants to the University of Rochester from the National Science Foundation, NASA/Ames, and the National Geographic Society. T. N. acknowledges the support of NSF Grant 84-20775 during the time of this work. C.E.W., T.J.J. and R.D.G were supported during the analysis of these data by NASA Contract NAGW 2324.

Funding Information:
1Visiting astronomer at the Infrared Telescope Facility, operated by the University of Hawaii, under contract from the National Aeronautics and Space Administration.


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