Central Bureau for Astronomical Telegrams
IAUC 4187: 1982i
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Circular No. 4187
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
PERIODIC COMET HALLEY (1982i)
Z. Sekanina, Jet Propulsion Laboratory, California Institute
of Technology, writes: "P/Halley's multiple-tail structure on Feb.
20-24, reported by West, Pedersen, and Gelly (IAUC 4179 and 4183),
by G. Garradd, Tamworth, N.S.W. (communicated via IHW Real Time
Monitor Network by C. S. Morris and J. E. Bortle, with further
information forwarded by D. A. Seargent via S. J. Edberg), and by R.
Royer, Lakewood, CA (via Edberg), is in fact a series of discrete
synchrones that are indicative of several isolated outbursts of
dust from the comet's nucleus. Tentatively I find the following
ejection times and particle accelerations beta-max that measure, in
units of solar attraction, the maximum effect of solar radiation
pressure on dust particles in the synchrones:
Outburst Time relative Maximum Number
No. to perihelion acceleration of obs.
(days) beta-max
1 -11.0 +/- 0.2 0.7 3
2 -6.9 +/- 0.1 1.8 4
3 -4.6 +/- 0.1 2.4 4
4 -3.9 +/- 0.2 2.2 1
5 +0.3 +/- 0.2 2.5 1
6 +0.9 +/- 0.2 2.0 2
7 +3.2 +/- 0.1 >3? 2
The quoted error of the ejection time is its estimated uncertainty,
based on a comparison of results from individual images and/or the
rate of position-angle change with ejection time. The existence of
outburst 7 is somewhat uncertain on account of its atypically-high
peak acceleration (possible contamination by the ion tail), but it
is corroborated by Ney and Knutson's (IAUC 4178) infrared observations,
showing that on Feb. 12.7 the comet was, on the average, 1.5
mag brighter than on Feb. 9.75 and 0.8 mag brighter than on Feb.
14.7. It is suggested that the dust was ejected from three different
locations of the surface, one source being common to events 1-
3; the second, to 4-5; and the third, to 6-7. If so, the outbursts
would recur with an average period of 52.5 +/- 1.6 hr and its
multiples. The broad tail's sunward boundary was reported to be at a
position angle of ~ 60P, in close agreement with my prediction in
The Comet Halley Handbook (2nd ed., p. 15)."
1986 March 4 (4187) Daniel W. E. Green
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