The YORP work was published in two separate papers in Science on 2007 April 13, after publication on Science Express on 2007 March 8. The work was described in a Cornell Chronicle story.
An image showing a rendering of asteroid 2000 PH5. The shape model was obtained by inverting high resolution radar images of the asteroid obtained at Arecibo and Goldstone. The shape model is published in Taylor et al., Science, in press (Image credit: Patrick Taylor, Cornell University).
Figure 1: Evolution of the position of 2000 PH5 in its Sun-Earth horseshoe orbit shown in a frame co-rotating with Earth. As the asteroid reaches alternate ends of the horseshoe every 100 years, it gravitationally bounces off Earth and reverses direction. The Sun is marked with (.) and the Earth is marked with (+). The 2003 trajectory is shown in red. (Image credit: Jean-Luc Margot, Cornell University)
2000 PH5 is a near-Earth object with an orbital period extremely similar to that of Earth. For the past ~100 years it had been trailing Earth while slowly catching up at a rate of about 3 degrees per year in mean longitude. The asteroid recently reached one end of its horseshoe orbit and underwent an abrupt change in orbital parameters. Earth's gravity increased the asteroid's orbital energy, such that the semi-major axis changed from its former value of ~0.994 AU to a value of ~1.006 AU. The asteroid will now recede at a rate of about 3 degrees per year in mean longitude, until it reaches the other end of the horseshoe, 30 degrees ahead of Earth, almost 100 years from now.
Patrick Taylor Department of Astronomy Cornell University 307 Space Sciences Bldg Ithaca, NY 14853 607 255 2727
Jean-Luc Margot Assistant Professor Department of Astronomy Cornell University 304 Space Sciences Bldg Ithaca, NY 14853 607 255 1810 http://www.astro.cornell.edu/~jlm
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