(66391) 1999 KW4
Simulated animation of 1999 KW4's rotation and moon.
|Discovery date||May 20, 1999|
|Epoch July 14, 2004 (JD 2453200.5)|
|Aphelion||1.084 AU (162.228 Gm)|
|Perihelion||0.200 AU (29.943 Gm)|
|0.642 AU (96.085 Gm)|
|188.017 d (0.51 a)|
Average orbital speed
|Dimensions||1.5 x 1.5 x 1.34 km (primary)|
|0–0.000 36 m/s² (variable)|
|0.000 72 km/s|
1999 KW4 has a moon orbiting it. The moon, designated S/2001 (66391) 1 or "1999 KW4 Beta", is ~360 m in diameter, and orbits 1999 KW4 '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. 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 around the object. As seen in the image at above right, the gravitational effects between the moon and the asteroid create a gigantic mountain extending laterally around the entire asteroid.
- Johnston, Wm. Robert, ed. (66391) 1999 KW4 January 7, 2007, retrieved May 3, 2007
- Margot, Jean-Luc, Another radar image of 1999 KW4 November1999, retrieved May 3, 2007
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