(66391) 1999 KW4
Simulated animation of 1999 KW4's rotation and moon.
|Discovery date||May 20, 1999|
|Minor planet category||Aten asteroid,
|Epoch July 14, 2004 (JD 2453200.5)|
|Aphelion||1.084 AU (162.228 Gm)|
|Perihelion||0.200 AU (29.943 Gm)|
|Semi-major axis||0.642 AU (96.085 Gm)|
|Orbital period||188.017 d (0.51 a)|
|Average orbital speed||37.16 km/s|
|Longitude of ascending node||244.934°|
|Argument of perihelion||192.597°|
|Dimensions||1.5 x 1.5 x 1.34 km (primary)|
|Mean density||2.0 g/cm³|
|Equatorial surface gravity||0–0.000 36 m/s² (variable)|
|Escape velocity||0.000 72 km/s|
|Rotation period||0.1152 d|
|Absolute magnitude (H)||16.5|
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.
One mission has been proposed to go and visit. MSGHQ, a small local aerospace company, plans to send an orbiter and a lander "like" Venera 3 onto its surface in about 2022–2026. It will be called Solstice 1 and about 11 more will come by the same asteroid. Solstice 1 and others will do a flyby of KW4 and its moon, then move off to 1999 TC36.
- NASA Jet Propulsion Laboratory Asteroid Radar Research, retrieved May 3, 2007
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