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A portrait of the nucleus of comet 67P/Churyumov-Gerasimenko

Lamy, Philippe L., Toth, Imre, Davidsson, Björn J.R., Groussin, Olivier, Gutiérrez, Pedro, Jorda, Laurent, Kaasalainen, Mikko, Lowry, Stephen C. (2007) A portrait of the nucleus of comet 67P/Churyumov-Gerasimenko. Space Science Reviews, 128 (1-4). pp. 23-66. ISSN 0038-6308. E-ISSN 1572-9672. (doi:10.1007/s11214-007-9146-x) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:52306)

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In 2003, comet 67P/Churyumov-Gerasimenko was selected as the new target of the Rosetta mission as the most suitable alternative to the original target, comet 46P/Wirtanen, on the basis of orbital considerations even though very little was known about the physical properties of its nucleus. In a matter of a few years and based on highly focused observational campaigns as well as thorough theoretical investigations, a detailed portrait of this nucleus has been established that will serve as a baseline for planning the Rosetta operations and observations. In this review article, we present a novel method to determine the size and shape of a cometary nucleus: several visible light curves were inverted to produce a size-scale free three-dimensional shape, the size scaling being imposed by a thermal light curve. The procedure converges to two solutions which are only marginally different. The nucleus of comet 67P/Churyumov-Gerasimenko emerges as an irregular body with an effective radius (that of the sphere having the same volume) = 1.72 km and moderate axial ratios a/b = 1.26 and a/c = 1.5 to 1.6. The overall dimensions measured along the principal axis for the two solutions are 4.49-4.75 km, 3.54-3.77 km and 2.94-2.92 km. The nucleus is found to be in principal axis rotation with a period = 12.4-12.7 h. Merging all observational constraints allow us to specify two regions for the direction of the rotational axis of the nucleus: RA = 220° +50° -30° and Dec = -70 ° ± 10 ° (retrograde rotation) or RA = 40° +50° -30° and Dec = +70 °± 10 ° (prograde), the better convergence of the various determinations presently favoring the first solution. The phase function, although constrained by only two data points, exhibits a strong opposition effect rather similar to that of comet 9P/Tempel 1. The definition of the disk-integrated albedo of an irregular body having a strong opposition effect raises problems, and the various alternatives led to a R-band geometric albedo in the range 0.045-0.060, consistent with our present knowledge of cometary nuclei. The active fraction is low, not exceeding ~ 7% at perihelion, and is probably limited to one or two active regions subjected to a strong seasonal effect, a picture coherent with the asymmetric behaviour of the coma. Our slightly downward revision of the size of the nucleus of comet 67P/Churyumov-Gerasimenko resulting from the present analysis (with the correlative increase of the albedo compared to the originally assumed value of 0.04), and our best estimate of the bulk density of 370 kg m -3, lead to a mass of ~ 8 � 10 12 kg which should ease the landing of Philae and insure the overall success of the Rosetta mission. © Springer Science+Business Media, Inc. 2007.

Item Type: Article
DOI/Identification number: 10.1007/s11214-007-9146-x
Additional information: Unmapped bibliographic data: LA - English [Field not mapped to EPrints] J2 - Space Sci Rev [Field not mapped to EPrints] AD - Laboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France [Field not mapped to EPrints] AD - Uppsala Observatory, Uppsala, Sweden [Field not mapped to EPrints] AD - Department of Astronomy, University of Maryland, College Park, MD, United States [Field not mapped to EPrints] AD - Instituto de Astrofísica de Andalucía-CSIC, Granada, Spain [Field not mapped to EPrints] AD - Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland [Field not mapped to EPrints] AD - Department of Physics and Astronomy, Queen's University, Belfast, United Kingdom [Field not mapped to EPrints] AD - Konkoly Observatory, Budapest, Hungary [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: 67P/Churyumov-Gerasimenko, Comet, Cometary nucleus, Rosetta space mission, Solar system, Density (specific gravity), Orbits, Planetary landers, Rotation, Space applications, Space rendezvous, Churyumov-Gerasimenko, Cometary nucleus, Comets, Rosetta space missions, Solar system
Subjects: Q Science > QB Astronomy
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Stephen Lowry
Date Deposited: 08 Dec 2015 22:59 UTC
Last Modified: 16 Nov 2021 10:21 UTC
Resource URI: (The current URI for this page, for reference purposes)

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