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(also written (66391) 1999 KW4) is an Aten and Mercury-crossing binary asteroid discovered by LINEAR in 1999. has a moon orbiting it. The moon, designated S/2001 (66391) 1 or " Beta", is ~360 m in diameter, and orbits 'Alpha' in 0.758 d (16 hours) at a distance of 2.6 km. The presence of a companion was suggested by photometric observations made June 19–27, 2000 by Petr Pravec and Lenka Šarounová at Observatoř Ondřejov (Ondřejov Observatory) and was confirmed by radar observations from Arecibo Observatory from May 21–23, 2001 by Lance A. M. Benner, Steven J. Ostro, Jon D. Giorgini, Raymond F. Jurgens, Jean-Luc Margot and Michael C. Nolan, announced on May 23, 2001.〔 The shapes of the two bodies and their dynamics are complex.〔NASA Jet Propulsion Laboratory (Asteroid Radar Research ), retrieved May 3, 2007〕 Among other bizarre properties, the equatorial regions of Alpha are very close to breakup: raising a particle a meter above the surface would put it into orbit. As seen in the image at above right, the gravitational effects between the moon and the asteroid create a gigantic mountain extending in the equatorial plane around the entire asteroid. On May 25, 2036, it will pass from Earth.〔 ==References== * Johnston, Wm. Robert, ed. ((66391) 1999 KW4 ) January 7, 2007, retrieved May 3, 2007 * Margot, Jean-Luc, (Another radar image of ) November1999, retrieved May 3, 2007 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「(66391) 1999 KW4」の詳細全文を読む スポンサード リンク
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