Steven J. Ostro, ^1* Petr Pravec, ² Lance A. M. Benner, ¹ R. Scott Hudson, ³ Lenka arounová, ² Michael D. Hicks, ¹ David L. Rabinowitz, ¹ James V. Scotti, ⁴ David J. Tholen, ⁵ Marek Wolf, ⁶ Raymond F. Jurgens, ¹ Michael L. Thomas, ¹ Jon D. Giorgini, ¹ Paul W. Chodas, ¹ Donald K. Yeomans, ¹ Randy Rose, ¹ Robert Frye, ¹ Keith D. Rosema, ¹ Ron Winkler, ¹ Martin A. Slade ¹

Observations of near-Earth asteroid 1998 KY26 shortly after its discovery reveal a slightly elongated spheroid with a diameter of about 30 meters, a composition analogous to carbonaceous chondritic meteorites, and a rotation period of 10.7 minutes, which is an order of magnitude shorter than that measured for any other solar system object. The rotation is too rapid for 1998 KY26 to consist of multiple components bound together just by their mutual gravitational attraction. This monolithic object probably is a fragment derived from cratering or collisional destruction of a much larger asteroid.

¹ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA.
² Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ondejov, Czech Republic.
³ School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA 99164-2752, USA.
⁴ Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
⁵ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA.
⁶ Astronomical Institute, Charles University Prague, V Holeovikách 2, CZ-18000 Prague, Czech Republic.
^*   To whom correspondence should be addressed. E-mail: ostro{at}reason.jpl.nasa.gov