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D. J. Tholen (Univ. Hawaii)
The Apollo-type asteroid 1998 KY26 was identified as an ideal target for the detection of the Yarkovsky effect (Vokrouhlicky et al. 2000, Icarus 148, 118). At the time of its 2024 close approach to the Earth, the displacement arising from the Yarkovsky effect could be as large as 4500 km. However, this 30 meter diameter near-Earth asteroid was observed for only 12 days in 1998, though there is a radar detection of it, and it was noted that the orbit uncertainties could be as large as the expected effect if the orbit is not carefully monitored. The brightest it will become prior to the 2024 close approach is V=23.4 in 2013. At the urging of S. Chesley, a special effort was made to observe this object during its 2002 opposition, when it reached only V=24.7, though the three sigma ephemeris uncertainty was only 16 arcsec. Time was requested and awarded on the University of Hawaii 2.24-m telescope near the time of greatest brightness for the object, and the weather cooperated, though the seeing was slightly worse than average for Mauna Kea. On each of two nights, nine separate exposures of 600 sec duration were taken, tracked at the asteroid's expected rate of motion. Careful processing and stacking of the nine frames did reveal the asteroid approximately 13 arcsec from its predicted location. The improved orbit effectively removes ephemeris uncertainty as a consideration for future observation attempts, leaving limiting magnitude as the only serious consideration. Although it is not yet possible to say anything about the size of the Yarkovsky effect on this object, it is possible that optical observations alone may reveal the effect as early as 2020, provided that continued astrometric observations are secured in at least 2009 and 2013.
This work was supported by NASA Grant NAG5-4524 to the University of Hawaii.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.