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Originally published in Science Express on 8 March 2007
Science 13 April 2007:
Vol. 316. no. 5822, pp. 274 - 277
DOI: 10.1126/science.1139038
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Reports

Spin Rate of Asteroid (54509) 2000 PH5 Increasing Due to the YORP Effect

Patrick A. Taylor,1* Jean-Luc Margot,1* David Vokrouhlicky,2 Daniel J. Scheeres,3 Petr Pravec,4 Stephen C. Lowry,5 Alan Fitzsimmons,5 Michael C. Nolan,6 Steven J. Ostro,7 Lance A. M. Benner,7 Jon D. Giorgini,7 Christopher Magri8

Radar and optical observations reveal that the continuous increase in the spin rate of near-Earth asteroid (54509) 2000 PH5 can be attributed to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, a torque due to sunlight. The change in spin rate is in reasonable agreement with theoretical predictions for the YORP acceleration of a body with the radar-determined size, shape, and spin state of 2000 PH5. The detection of asteroid spin-up supports the YORP effect as an explanation for the anomalous distribution of spin rates for asteroids under 10 kilometers in diameter and as a binary formation mechanism.

1 Department of Astronomy, Cornell University, Ithaca, NY 14853–6801, USA.
2 Institute of Astronomy, Charles University, V Holesovickách 2, 18000 Prague 8, Czech Republic.
3 Department of Aerospace Engineering, University of Michigan, 1320 Beal Avenue, Ann Arbor, MI 48109–2140, USA.
4 Astronomical Institute, Academy of Sciences of the Czech Republic, Fricova 1, CZ-25165 Ondrejov, Czech Republic.
5 School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
6 Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612, USA.
7 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109–8099, USA.
8 University of Maine at Farmington, 173 High Street, Preble Hall, Farmington, ME 04938, USA.

* To whom correspondence should be addressed. E-mail: ptaylor{at}astro.cornell.edu (P.A.T.); jlm{at}astro.cornell.edu (J.L.M.)

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Science. ISSN 0036-8075 (print), 1095-9203 (online)