Asteroid 2002 AA29

Resources

Late in 2002, astronomers and the International Astronomical Union (IAU) confirmed the discovery the discovery of an asteroid, designated Asteroid 2002 AA29, in a companion orbit to Earth. It was the first object ever identified to be in a companion orbit around the sun (i.e., it shares at least some of the same orbital path and space). In another 600 years, the asteroid will technically and temporarily become an Earth moon.

Although in a companion orbit, computer driven mathematical estimates establish that Asteroid 2002 AA29 never comes closer than approximately 3.5 million mi (5.6 million km from Earth at its closest approach.

Asteroid 2002 AA29 was first detected by the linear automated sky survey project in January 2002. Optical and gravitational evidence indicate that Asteroid 2002 AA29 is approximately 109 yd (100 m) wide.

Although co-orbital for some of its travel around the Sun, Asteroid 2002 AA29 does not follow the exact same path as Earth. Asteroid 2002 AA29 travels a horseshoe-like path that allows it vary in relative position to the sun and Earth (i.e., it oscillates between appearing on both sides of the Sun from Earth’s perspective. Asteroid 2002 AA29 made its closest recent approach to Earth—approximately 10 to 12 times the normal Earth-moon distance—at 1900 GMT on January 8, 2003.

Orbital dynamics projections establish that in 550 AD Asteroid 2002 AA29 technically became an Earth orbital satellite—technically a second moon. Because of Asteroid 2002 AA29’s odd orbit this event is due to occur again in 2600 and will last approximately 50 years.

Resources

Brasser, R., et al. “Transient Co-Orbital Asteroids.” Icarus. 171 (2004): 102-109.

OTHER

NASA Near Earth Object Program. 2002 AA29 Animations. <http://neo.jpl.nasa.gov/2002aa29.html> (accessed October 17, 2006).