Dynamical Configuration of Binary Near-Earth Asteroid (66391) 1999 KW4

Scheeres, D. J.
Fahnestock, E. G.
Ostro, S. J.
Margot, J.-L.
Benner, L. A. M.
Broschart, S. B.
Bellerose, J.
Giorgini, J. D.
Nolan, M. C.
Magri, C.
Pravec, P.
Scheirich, P.
Rose, R.
Jurgens, R. F.
De Jong, E. M.
Suzuki, S.

¹Department of Aerospace Engineering, University of Michigan, 1320 Beal Avenue, Ann Arbor, MI 48109-2140, USA. ²Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA. ³Department of Astronomy, Cornell University, 304 Space Sciences Building, Ithaca, NY 14853, USA. ⁴Arecibo Observatory, HC03 Box 53995, Arecibo, Puerto Rico 00612, USA. ⁵Department of Natural Sciences, University of Maine at Farmington, 173 High Street, Farmington, ME 04938, USA. ⁶Astronomical Institute, Academy of Sciences of the Czech Republic Fričova 1, CZ-25165 Ondřejov, Czech Republic.

*To whom correspondence should be addressed. E-mail: [email protected]

Supporting Online Material: www.sciencemag.org/cgi/content/full/1133599/DC1; SOM Text; Figs. S1 to S4; References and Notes; Movie S1

8 August 2006; accepted 4 October 2006

Published online 12 October 2006; 10.1126/science.1133599

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Science 314(5803):p 1280-1283, November 24, 2006.

Dynamical simulations of the coupled rotational and orbital dynamics of binary near-Earth asteroid 66391 (1999 KW4) suggest that it is excited as a result of perturbations from the Sun during perihelion passages. Excitation of the mutual orbit will stimulate complex fluctuations in the orbit and rotation of both components, inducing the attitude of the smaller component to have large variation within some orbits and to hardly vary within others. The primary's proximity to its rotational stability limit suggests an origin from spin-up and disruption of a loosely bound precursor within the past million years.