Comet 46P/Wirtanen
Abstract
T. L. Farnham, M. M. Knight, University of Maryland, College Park; and D. G. Schleicher, Lowell Observatory, Flagstaff, report results from observations of comet 46P from the Lowell Observatory Discovery Channel Telescope and Hall 1.07-m telescope. A sequence of enhanced narrowband CN images, obtained during Nov. 1-4 and supplemented by an image from the Lowell 0.79-m telescope on Oct. 28, reveal at least two rotating spiral-arc structures in the coma. Images obtained on Nov. 1, 2, and 4 show nearly identical morphology, with the first pair indicating that the rotation period is a sub-multiple of about 26.5 hr. The sequence of images was phased to periods around 13.3, 8.8, 6.6, 5.3 and 4.4 hours, with the smoothest apparent motion resulting for a value of 8.91 +/- 0.03 hr, which is assumed to represent the rotation period of the nucleus. There is a small possibility that the period is 13.4 hr, though this would require three active areas, equally spaced in longitude, with two of them exhibiting nearly identical behavior. All other sub-multiples produced unacceptable results. The near-identical appearance in the morphology after as many as eight rotations supports the assumptions that the rotation period is constant and the nucleus is in a state of simple rotation. Visual total-magnitude and coma-diameter estimates: Sept. 10.10 UT, 12.4, 1'.5 (J. J. Gonzalez, Leon, Spain, 0.20-m reflector); 20.05, 13.7, 0'.5 (W. Hasubick, Buchloe, Germany, 44-cm reflector); Oct. 4.00, 10.6, 4' (Gonzalez); 6.21, 11.4, 2' (M. Goiato, Aracatuba, Brazil, 0.22-m reflector); 6.61, 11.4, 1'.7 (S. Yoshida, Gunma, Japan, 0.40-m reflector); 7.71, 11.9, 3'.0 (Yoshida); 13.21, 10.3, 4' (Goiato); 16.07, 9.6, 7' (Gonzalez); 20.11, 9.2, 8' (Gonzalez); 30.09, 8.2, 12' (Goiato, 7x50 binoculars); 31.09, 8.1, 14' (Goiato); Nov. 3.63, 8.5, 7' (Yoshida); 4.01, 7.4, 15' (J. J. Gonzalez, Leon, Spain, 10x50 binoculars); 6.06, 7.8, 20' (Goiato).
- Publication:
-
Central Bureau Electronic Telegrams
- Pub Date:
- November 2018
- Bibcode:
- 2018CBET.4571....1F