WISE/NEOWISE Observations of Comet 103P/Hartley 2

Creators: Bauer, James M.; Walker, Russell G.; Mainzer, A. K.; Masiero, Joseph R.; Grav, Tommy; Dailey, John W.; McMillan, Robert S.; Lisse, Carey M.; Fernandez, Yan R.; Meech, Karen J.; Pittichova, Jana; Blauvelt, Erin K.; Masci, Frank J.; A'Hearn, Michael F.; Cutri, Roc M.; Scotti, James V.; Tholen, David J.; DeBaun, Emily; Wilkins, Ashlee; Hand, Emma; Wright, Edward L.; WISE Team

Abstract

We report results based on mid-infrared photometry of comet 103P/Hartley 2 taken during 2010 May 4-13 (when the comet was at a heliocentric distance of 2.3 AU, and an observer distance of 2.0 AU) by the Wide-field Infrared Survey Explorer. Photometry of the coma at 22 μm and data from the University of Hawaii 2.2 m telescope obtained on 2010 May 22 provide constraints on the dust particle size distribution, d log n/d log m, yielding power-law slope values of alpha = –0.97 ± 0.10, steeper than that found for the inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. The extracted nucleus signal at 12 μm is consistent with a body of average spherical radius of 0.6 ± 0.2 km (one standard deviation), assuming a beaming parameter of 1.2. The 4.6 μm band signal in excess of dust and nucleus reflected and thermal contributions may be attributed to carbon monoxide or carbon dioxide emission lines and provides limits and estimates of species production. Derived carbon dioxide coma production rates are 3.5(± 0.9) × 10^(24) molecules per second. Analyses of the trail signal present in the stacked image with an effective exposure time of 158.4 s yields optical-depth values near 9 × 10^(–10) at a delta mean anomaly of 0.2 deg trailing the comet nucleus, in both 12 and 22 μm bands. A minimum chi-squared analysis of the dust trail position yields a beta-parameter value of 1.0 × 10^(–4), consistent with a derived mean trail-grain diameter of 1.1/ρ cm for grains of ρ g cm^(–3) density. This leads to a total detected trail mass of at least 4 × 10^(10) ρ kg.

Additional Information

© 2011 The American Astronomical Society. Received 2011 April 10; accepted 2011 June 21; published 2011 August 23. This publication makes use of data products from the Widefield Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publication also makes use of data products from NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration. Observing time was allocated at the University of Hawaii 88 inch telescope at Mauna Kea Observatory, the Palomar Observatory Hale 200 inch telescope, by the National Optical Astronomy Observatory at the SOAR telescope, and on Steward Observatory's 2.3mon Kitt Peak. The SOAR Telescope is a joint project of Conselho Nacional de Pesquisas Cientificas e Tecnologicas CNPq-Brazil, The University of North Carolina at Chapel Hill, Michigan State University, and the National Optical Astronomy Observatory. The Hale Telescope at Palomar Observatory is operated as part of a collaborative agreement between the California Institute of Technology, its divisions Caltech Optical Observatories and the Jet Propulsion Laboratory (operated for NASA), and Cornell University. J.M.B. thanks Dr. M. Hanner for her valuable advice on the analysis and the anonymous reviewer for their helpful comments.

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