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Triplicity and physical characteristics of Asteroid (216) Kleopatra |
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| Authors: | P. Descamps,F. Marchis,J. Berthier,G. Duchê ne,I. de Pater,L. Lim,F. Vachier,J.-P. Teng-Chuen-Yu,J. Pollock,R. Vieira-Martins,J.I.B. Camargo,F. Braga-Ribas,B. Macomber |
| Affiliation: | a Institut de Mécanique Céleste et de Calcul des Éphémérides, Observatoire de Paris, UMR8028 CNRS, 77 av. Denfert-Rochereau 75014 Paris, France b University of California at Berkeley, Department of Astronomy, 601 Campbell Hall, Berkeley, CA 94720, USA c University of Tennessee at Knoxville, 306 EPS Building, 1412 Circle Drive, Knoxville, TN 37996, USA d Université Joseph Fourier, Grenoble 1/CNRS, Laboratoire d’Astrophysique de Grenoble (LAOG), UMR5571, BP 53, 38041 Grenoble Cedex 09, France e Space Science Institute, Boulder, CO 80303, USA f Wiggins Observatory, 472 Country Club, Tooele, UT 84074_9665, USA g Makes Observatory, 18, rue G. Bizet, Les Makes, 97421 La Rivière, France h Appalachian State University, Department of Physics and Astronomy, 231 CAP Building, Boone, NC 28608, USA i Observatório do Valongo/UFRJ - Universidade Federal do Rio de Janeiro, Rua Ladeira Pedro Antonio, 43 CEP 20080-090 Rio de Janeiro, Brazil j Observatório Nacional/MCT, R. Gal. José Cristino 77, CEP20921-400 RJ, Brazil k SETI Institute, Carl Sagan Center, 515 N. Whisman Road, Mountain View, CA 94043, USA |
| Abstract: | To take full advantage of the September 2008 opposition passage of the M-type Asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO) imaging with the W.M. Keck II telescope to capture unprecedented high resolution images of this unusual asteroid. Our AO observations with the W.M. Keck II telescope, combined with Spitzer/IRS spectroscopic observations and past stellar occultations, confirm the value of its IRAS radiometric radius of 67.5 km as well as its dog-bone shape suggested by earlier radar observations. Our Keck AO observations revealed the presence of two small satellites in orbit about Kleopatra (see Marchis, F. et al. [2008a]. (3749) Balam. In: Green, D.W.E. (Ed.), IAU Circ. 8928; Marchis, F., Descamps, P., Berthier, J., Emery, J.P. [2008b]. S/2008 ((216)) 1 and S/2008 ((216)) 2. In: Green, D.W.E. (Ed.), IAU Circ. 8980). Accurate measurements of the satellite orbits over a full month enabled us to determine the total mass of the system to be 4.64 ± 0.02 × 1018 kg. This translates into a bulk density of 3.6 ± 0.4 g/cm3, which implies a macroscopic porosity for Kleopatra of ∼30-50%, typical of a rubble-pile asteroid. From these physical characteristics we measured its specific angular momentum, very close to that of a spinning equilibrium dumbbell. |
| Keywords: | Asteroids Satellites of asteroids Adaptive optics Photometry Orbit determination |
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