Circular No. 8909
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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COMET 8P/TUTTLE
     J. K. Harmon, M. C. Nolan, and E. S. Howell, Arecibo
Observatory; and J. D. Giorgini, Jet Propulsion Laboratory,
obtained 300-m-resolution radar imaging of comet 8P/Tuttle on Jan.
2-4 using the Arecibo Observatory 12.6-cm planetary radar.  The
nucleus is a strongly bifurcated object, possibly a contact binary,
with two roughly spherical lobes measuring 3 and 4 km in diameter
(+/- 25 percent).  Following the changing rotation aspect from
night to night and within the 2.5-hr observing sessions gives a
preliminary estimate of 7.7 ± 0.2 hr for the rotation period.  In
addition to the nucleus echo, there is a weak echo component from
large (> cm-sized) coma grains.
     Visual total-magnitude and coma-diameter estimates by J. J.
Gonzalez, Asturias, Spain:  2007 Dec. 26.77, 6.1, 15' (6x30
binoculars); 30.79, 5.6, 25' (naked eye); 2008 Jan. 3.79, 5.1, 30'
(naked eye); 6.78, 5.2, 30' (4x30 monocular); 9.84, 5.3, 30' (naked
eye).



                      (C) Copyright 2008 CBAT
2008 January 11                (8909)            Daniel W. E. Green