The newly discovered asteroid 2002 AA_(29) moves in a very Earth-like orbit that relative to Earth has a unique horseshoe shape and allows transitions to a quasi-satellite state. This is the first body known to be in a simple heliocentric horseshoe orbit, moving along its parent planet's orbit. It is similarly also the first true co-orbital object of Earth, since other asteroids in 1:1 resonance with Earth have orbits very dissimilar from that of our planet. When a quasi-satellite, it remains within 0.2 AU of the Earth for several decades. 2002 AA_(29) is the first asteroid known to exhibit this behavior. 2002 AA_(29) introduces an important new class of objects offering potential targets for space missions and clues to asteroid orbit transfer evolution.
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