2002 AA29

2002 AA₂₉

Discovery[1]
Discovered by	LINEAR
Discovery date	January 9, 2002
Designations
Alternative designations	none
Minor planet category	Aten asteroid
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc	736 days (2.02 yr)
Aphelion	1.0055 AU (150.42 Gm)
Perihelion	0.97963 AU (146.551 Gm)
Semi-major axis	0.99259 AU (148.489 Gm)
Eccentricity	0.013047
Orbital period (sidereal)	0.99 yr (361.2 d)
Average orbital speed	29.784 km/s
Mean anomaly	310.32°
Mean motion	0° 59m 48.012s /day
Inclination	10.748°
Longitude of ascending node	106.38°
Argument of perihelion	101.75°
Earth MOID	0.0116565 AU (1.74379 Gm)
Jupiter MOID	3.96814 AU (593.625 Gm)
Physical characteristics
Dimensions	~0.06 km <100 metres[3] 25±5 metres[4]
Mass	~2.3×108 kg
Mean density	2 ? g/cm3
Equatorial surface gravity	~0.000 017 m/s2
Equatorial escape velocity	~0.000 032 km/s
Synodic rotation period	0.55 h (33 min)[2]
Geometric albedo	0.2 ?
Temperature	~279 K
Spectral type	S-type asteroid[4]
Absolute magnitude (H)	24.1

2002 AA₂₉ (also written 2002 AA29) is a small near-Earth asteroid that was discovered on January 9, 2002 by the LINEAR (Lincoln Near Earth Asteroid Research) automatic sky survey. The diameter of the asteroid is only about 20–100 metres (70–300 ft). It revolves about the Sun on an almost circular orbit very similar to that of the Earth. This lies for the most part inside the Earth's orbit, which it crosses near the asteroid's furthest point from the Sun, the aphelion. Because of this orbit, the asteroid is classified as Aten type,^[2] named after the asteroid 2062 Aten.

A further characteristic is that its mean orbital period about the Sun is exactly one sidereal year. This means that it is locked into a relationship with the Earth, since such an orbit is only stable under particular conditions. As yet only a few asteroids of this sort are known, locked into a 1:1 resonance with the Earth. The first was 3753 Cruithne, discovered in 1986.

Asteroids that have a 1:1 orbital resonance with a planet are also called co-orbital objects, because they follow the orbit of the planet. The most numerous known co-orbital asteroids are the so-called trojans, which occupy the L4 and L5 Lagrangian points of the relevant planet. However, 2002 AA₂₉ does not belong to these. Instead, it follows a so-called horseshoe orbit along the path of the Earth.