4179 Toutatis

4179 Toutatis
	Toutatis imaged by Chang'e 2 during its flyby
Discovery
Discovered by	Christian Pollas
Discovery site	Caussols
Discovery date	4 January 1989
Designations
MPC designation	(4179) Toutatis
Pronunciation	/taʊˈteɪtɪs/
Named after	Toutatis (Celtic mythology)
Alternative designations	1989 AC; 1934 CT;
Minor planet category	NEO; Apollo; PHA ; Alinda; Mars-crosser;
Adjectives	Toutatian
Orbital characteristics
	Epoch 27 November 2008 (JD 2454797.5)
	Uncertainty parameter 0
Observation arc	83.29 yr (30,422 days)
Earliest precovery date	10 February 1934
Aphelion	4.1242 AU
Perihelion	0.9399 AU
Semi-major axis	2.5321 AU
Eccentricity	0.6288
Orbital period (sidereal)	4.03 yr (1,472 days)
Mean anomaly	5.1220°
Mean motion	0° 14m 40.56s / day
Inclination	0.4460°
Longitude of ascending node	124.30°
Argument of perihelion	278.75°
Earth MOID	0.0064 AU (2.5 LD)
Physical characteristics
Dimensions	4.75 × 1.95 km; 4.26 × 2.03 × 1.70 km;
Mean diameter	2.45 km
Mass	1.9×1013 kg
Mean density	2.5 g/cm3
Synodic rotation period	176 h (7.3 d)
Geometric albedo	0.13
Spectral type	Sk (SMASSII)
Apparent magnitude	8.8–22.4
Absolute magnitude (H)	15.30

4179 Toutatis (provisional designation 1989 AC) is an elongated, stony asteroid and slow rotator, classified as a near-Earth object and potentially hazardous asteroid of the Apollo asteroid group, approximately 2.5 kilometers in diameter. Discovered by French astronomer Christian Pollas at Caussols in 1989, the asteroid was named after Toutatis from Celtic mythology.

Toutatis is also a Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with the planet Jupiter, a 1:4 resonance with the planet Earth, and frequent close approaches to the terrestrial planets, including Earth. In December 2012, Toutatis passed within about 18 lunar distances of Earth. The Chinese lunar probe Chang'e 2 flew by the asteroid at a distance of 3.2 kilometers and a relative velocity of 10.73 km/s. Toutatis approached Earth again in 2016, but will not make another notably close approach until 2069.

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