DPS Pasadena Meeting 2000, 23-27 October 2000
Session 13. Asteroids II - Discovery and Dynamics
Oral, Chairs: W. Merline, J. Burns, Tuesday, 2000/10/24, 8:30-10:00am, C106

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[13.08] The Geometry of Keyholes

G.B. Valsecchi (IAS-CNR), A. Milani, G.F. Gronchi (Univ. Pisa), S.R. Chesley (JPL)

The term `keyhole' has been introduced by Chodas (1999) to denote the small regions of the b-plane of a specific close encounter of an asteroid with, say, the Earth, having the property that, if the asteroid passes through one of them, it will hit the planet at a subsequent encounter.

Using Öpik's theory of close encounters, it is possible to show that keyholes leading to a primary resonant or non-resonant return are described by a very simple geometry, and their location on the b-plane is given by very simple analytical expressions. The theory allows also to describe the size and shape of the keyholes, and to find the way in which secondary keyholes are nested within primary ones.

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