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Dr. Giovanni Valsecchi

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Dr. Giovanni Valsecchi is Senior Scientist at the Institute for Space Astrophysics and Planetology in Rome. Born in Taranto (Italy), 29 April 1951, he got the Laurea in Physics at the University of Rome "La Sapienza" in 1975, cum laude.

His research activity is centred on the dynamics of small Solar System bodies, with special emphasis on the orbital evolution of comets and of planet-crossing asteroids affected by planetary close encounters. Besides this, he is interested in the dynamics of meteoroid streams, of space debris, and in some peculiar aspects of the Main Lunar Problem.

He has been member of the Solar System Working Group of ESA (1991-1994), and of the Scientific Council of the Istituto Nazionale di Astrofisica (2005-2007); within the International Astronomical Union he has been President Commission 20 (Positions & Motions of Minor Planets, Comets & Satellites, 2003-2006), Vice-President of Division III (Planetary Systems Sciences, 2009-2012) and, after the 2012 restructuring of IAU Divisions, is currently President of Division F (Planetary Systems and Bioastronomy, 2012-2015). He organized, with A. Carusi, IAU Colloquium 83 "Dynamics of Comets: their Origin and Evolution" (Rome, 1984), and co-edited the Proceedings; he also organized, with A. Milani and D. Vokrouhlicky, IAU Symposium 236 "Near Earth Objects, our Celestial Neighbors: Opportunity and Risk", Prague, 2006, and co-edited the Proceedings. Asteroid (3725) is named Valsecchi.


An analytical theory of close encounters and keyholes

The term `keyhole' denotes a small region 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 it, it will hit the planet at a subsequent encounter. Using an extension of Opik's theory of close encounters (Valsecchi, Milani, Gronchi and Chesley, Astron. Astrophys. 408, 1179-1196, 2003), 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 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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