CLOSE APPROACHES OF ASTEROID 1999 AN₁₀:
RESONANT AND NON-RESONANT RETURNS

Andrea Milani, Steven R. Chesley
Dipartimento di Matematica, Università di Pisa
Via Buonarroti 2
56127 PISA, ITALY
E-mail: milani@dm.unipi.it, chesley@dm.unipi.it

Giovanni B. Valsecchi
IAS-Planetologia
Area di ricerca CNR
Via Fosso del Cavaliere
00133 ROMA, ITALY
E-mail: giovanni@ias.rm.cnr.it

12 May 1999

Abstract:

The Earth passes very close to the orbit of the asteroid 1999 AN₁₀ twice per year, but whether or not this asteroid can have a close approach depends upon the timing of its passage across the ecliptic plane. Among the possible orbits there are some with a close approach in 2027. The period of the asteroid may be perturbed in such a way that it returns to an approach to the Earth at either of the possible encounter points. We have developed a theory which successfully predicts the 25 possible such returns up to 2040. We have also identified 6 more close approaches resulting from the cascade of successive returns. Because of this extremely chaotic behaviour there is no way to predict all possible approaches for more than a few decades after any close encounter, but the orbit will remain dangerously close to the orbit of the Earth for about 600 years.