Arecibo S-band (2380 MHz, 13 cm) and Goldstone X-band (8560 MHz, 3.5 cm) radar observations from 2001, 2004, and 2005  along with precise optical observations  reveal that the observed change in spin rate of near-Earth asteroid (54509) YORP, formerly 2000 PH5, is due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, a torque due to sunlight. The increase in sidereal spin rate of (2.0 ± 0.2) x 10-4 deg/day2 , equivalently a shortening of the sidereal spin period by just over one millisecond per year, is in reasonable agreement with theoretical predictions for the YORP acceleration of a body with the radar-determined size, shape, and spin state of asteroid (54509) YORP. The detection of asteroid spin-up supports the YORP effect as an explanation for the anomalous distribution of spin rates for asteroids under 10 km in diameter and as a binary formation mechanism.  P. A. Taylor et al., Science, 316, 2007.  S. C. Lowry et al., Science, 316, 2007.
|Publication status||Published - 01 Oct 2007|