The nuclei of comets 7P/Pons-Winnecke, 14P/Wolf and 92P/Sanguin

APS Division, School of Physics and Astronomy, Queen's University Belfast, Belfast BT7 1NN, UK e-mail: C.Snodgrass@qub.ac.uk

Received: 13 April 2005
Accepted: 16 August 2005

Abstract

Jupiter Family comets (JFCs) are short period comets which have recently entered the inner solar system, having previously orbited in the Kuiper Belt since the formation of the planets. We used two nights on the 3.6 m New Technology Telescope (NTT) at the European Southern Observatory, to obtain VRI photometry of three JFCs; 7P/Pons-Winnecke, 14P/Wolf and 92P/Sanguin. These were observed to be stellar in appearance. We find mean effective radii of  km for 7P,  km for 14P and  km for 92P, assuming a geometric albedo of 0.04. From light-curves for each comet we find rotation periods of and  h for 14P and 92P respectively. 7P exhibits brightness variations which imply a rotation period of  h. Assuming the nuclei to be ellipsoidal the measured brightness variations imply minimum axial ratios of for 7P and for both 14P and 92P. This in turn implies minimum densities of  g cm^-3 for 7P,  g cm^-3 for 14P and  g cm^-3 for 92P. Finally, we measure colour indices of and for 7P/Pons-Winnecke, and for 14P/Wolf, and and for 92P/Sanguin.