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Astron. Astrophys. 346, L65-L68 (1999)

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Letter to the Editor

Close approaches of asteroid 1999 AN10: resonant and non-resonant returns

Andrea Milani 1, Steven R. Chesley 1 and Giovanni B. Valsecchi 2

1 Dipartimento di Matematica, Università di Pisa, Via Buonarroti 2, I-56127 Pisa, Italy (milani@dm.unipi.it, chesley@dm.unipi.it)
2 IAS-Planetologia, Area di ricerca CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy (giovanni@ias.rm.cnr.it)

Received 13 April 1999 / Accepted 14 May 1999


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.

Key words: minor planets, asteroids – chaos

© European Southern Observatory (ESO) 1999

Online publication: June 17, 1999