Techniques d'observation spectroscopique d'astéroïdes

CHAPTER 1. WHY ASTEROIDS? 37
tel-00785991, version 1 - 7 Feb 2013
Owing to some mechanisms some of the Main Belt Asteroids have migrated into the inner
part of the Solar System [Morbidelli et al., 2002]. These are Near-Earth Asteroids (denoted
NEAs), small bodies of the Solar System with perihelion distances q ≤ 1.3 AU and aphelion
distances Q≥0.983AU, whose orbits approach or intersect Earth orbit. Dynamical studies confirmed
the main belt origin for the majority of NEAs population. The transition of a main belt
asteroid to NEA class is due to the dynamical perturbations associated with the main belt resonances.
The most active of these regions acting as escape hatches are the ν6 secular resonance
and the orbital resonances 3:1, 5:2 and 2:1 with Jupiter situated at 2.5, 2.8 et 3.2 astronomical
units. Long term numerical integrations have revealed the source regions of the current NEAs
population: 61% originated in the inner region of main belt, 24% in the central and 8% in the
outer main belt. Only 6% of NEAs are considered to have a cometary origin. The steady-state
model of NEA will require a constant flux of objects with H≤18 of 800/Myr.
Depending on their orbital parameters, NEAs are subdivided into Amors (1.016 < q < 1.3
AU), Apollos (a ≥ 1.0 AU; q ≤ 1.016 AU), Athens (semi-major axe a < 1.0 AU; Q ≥ 0.983
AU), and Atiras (Q