(277475) 2005 WK4

(277475) 2005 WK₄, provisional designation 2005 WK₄, is a stony, sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group that passed Earth within 8.2 lunar distances on 8 August 2013.^[7] It was discovered on 27 November 2005, by astronomers of the Siding Spring Survey at Siding Spring Observatory, Australia.^[2]

(277475) 2005 WK₄

2005 WK4 imaged 30 times by radar at Goldstone on 8 August 2013
Discovery[1][2]
Discovered by	Siding Spring Srvy.
Discovery site	Siding Spring Obs.
Discovery date	27 November 2005
Designations
MPC designation	(277475) 2005 WK4
Alternative designations	2005 WK4
Minor planet category	Apollo · NEO · PHA[1][2]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	8.71 yr (3,180 days)
Aphelion	1.2506 AU
Perihelion	0.7707 AU
Semi-major axis	1.0106 AU
Eccentricity	0.2374
Orbital period (sidereal)	1.02 yr (371 days)
Mean anomaly	81.040°
Mean motion	0° 58m 12.36s / day
Inclination	9.8433°
Longitude of ascending node	138.14°
Argument of perihelion	74.063°
Earth MOID	0.0037 AU · 1.4 LD
Physical characteristics
Dimensions	0.25±0.05 km[a] 0.284 km (calculated)[3]
Synodic rotation period	2.595±0.002 h[4] 2.7±0.1 h[a] 2.73±0.05 h[5]
Geometric albedo	0.20 (assumed)[3]
Spectral type	Sk[6] · S (assumed)[3] B–V = 0.677±0.025[6] V–R = 0.446±0.019[6] V–I = 0.750±0.024[6]
Absolute magnitude (H)	20.1[1][3]

Description

In August 2013, 2005 WK₄ was radar-imaged by the Deep Space Network dish at Goldstone Observatory, United States,^[7] and had been observed previously at Arecibo Observatory in July 2012 (this was not a close approach though).^[8]

Physical characteristics

2005 WK₄ measures approximately 250 meters in diameter, and has a rotation period of 2.595 hours.^[3][4][a] Its spectral type is that of an Sk-subtype, which transitions from the stony S-type to the uncommon K-type asteroids.^[6]

See also

• List of asteroid close approaches to Earth in 2013

Notes

1. Benner (2013): radiometric observations: mean diameter 0.25±0.05 km; rotation period 2.7±0.1 hours. Summary figures at the LCDB; also see NASA news report