(66391) 1999 KW4

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(66391) 1999 KW4
1999 KW4 animated.gif
Simulated animation of 1999 KW4's rotation and moon.
Discovery
Discovered by LINEAR
Discovery date May 20, 1999
Designations
none
Aten asteroid,
Mercury-crosser asteroid,
Venus-crosser asteroid
Orbital characteristics
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)
Eccentricity 0.688
188.017 d (0.51 a)
37.16 km/s
168.533°
Inclination 38.890°
244.934°
192.597°
Physical characteristics
Dimensions 1.5 x 1.5 x 1.34 km (primary)
Mass 2.4×1012 kg
Mean density
2.0 g/cm³
0–0.000 36 m/s² (variable)
0.000 72 km/s
0.1152 d
Albedo 0.15
Temperature 250–600 K
16.5

(66391) 1999 KW4 (also written (66391) 1999 KW4) is an Aten and Mercury-crossing binary asteroid[1] discovered by LINEAR in 1999.

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)[citation needed] 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.[1]

The shapes of the two bodies and their dynamics are complex.[2] 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.

On May 25, 2036 it will pass 0.0155 AU (2,320,000 km; 1,440,000 mi) from Earth.[3]


Radar images of 1999 KW4 taken by NASA's Goldstone Observatory.

References[edit]

  1. ^ a b Johnston, Robert. "(66391) 1999 KW4". johnstonsarchive.net. Retrieved 29 May 2015. 
  2. ^ NASA Jet Propulsion Laboratory Asteroid Radar Research, retrieved May 3, 2007
  3. ^ "JPL Close-Approach Data: 66391 (1999 KW4)" (2013-05-09 last obs (arc=14.9 yr)). Retrieved 2014-03-02.