Ostro Steven J, Margot Jean-Luc, Benner Lance A M, Giorgini Jon D, Scheeres Daniel J, Fahnestock Eugene G, Broschart Stephen B, Bellerose Julie, Nolan Michael C, Magri Christopher, Pravec Petr, Scheirich Petr, Rose Randy, Jurgens Raymond F, De Jong Eric M, Suzuki Shigeru
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA.
Science. 2006 Nov 24;314(5803):1276-80. doi: 10.1126/science.1133622. Epub 2006 Oct 12.
High-resolution radar images reveal near-Earth asteroid (66391) 1999 KW4 to be a binary system. The approximately 1.5-kilometer-diameter primary (Alpha) is an unconsolidated gravitational aggregate with a spin period approximately 2.8 hours, bulk density approximately 2 grams per cubic centimeter, porosity approximately 50%, and an oblate shape dominated by an equatorial ridge at the object's potential-energy minimum. The approximately 0.5-kilometer secondary (Beta) is elongated and probably is denser than Alpha. Its average orbit about Alpha is circular with a radius approximately 2.5 kilometers and period approximately 17.4 hours, and its average rotation is synchronous with the long axis pointed toward Alpha, but librational departures from that orientation are evident. Exotic physical and dynamical properties may be common among near-Earth binaries.
高分辨率雷达图像显示，近地小行星(66391)1999 KW4是一个双星系统。直径约1.5公里的主星(阿尔法)是一个松散的引力聚集体，自转周期约2.8小时，体密度约每立方厘米2克，孔隙率约50%，呈扁球形，在物体势能最小处由赤道脊主导。直径约0.5公里的次星(贝塔)呈细长形，可能比阿尔法密度更大。它绕阿尔法的平均轨道是圆形的，半径约2.5公里，周期约17.4小时，其平均自转与指向阿尔法的长轴同步，但明显存在偏离该方向的摆动。奇特的物理和动力学特性在近地双星中可能很常见。
