Sources And Populations Of Near-earth Objects: Recent Findings And Historical Implications

Abstract of talk by Mark E. Bailey

Armagh Observatory, College Hill, Armagh, BT61 9DG, meb[at]
Presented at the SIS Conference: Natural Catastrophes during Bronze Age Civilisations (11th-13th July 1997)

Near-Earth objects (NEOs) comprise a heterogeneous population of objects from a variety of sources ranging from long-period comets to the main asteroid belt. Recent dynamical results show that the orbits are chaotic, and that comets may in principle evolve into orbits similar to those of objects usually classified as asteroids (and vice-versa), and that comets and asteroids may resemble one another depending on the phase of their physical evolution and heliocentric distance. This paper reviews progress towards understanding the nature of the NEO population, particularly whether the source flux is principally cometary or asteroidal, and assesses the question of probable time-dependence in the flux and size distribution of the impacting objects. Evidence for impacts in the astronomically recent past and of historical variations in the NEO population will be briefly discussed.

MARK E BAILEY is an astrophysicist and Director of the Armagh Observatory. His current research interests include the dynamical evolution of comets, asteroids and meteoroid streams; solar-system terrestrial interrelationships; and the implications of the cometary and meteoroid impact hazard. Asteroid (4050), discovered in 1976 by C.-I. Lagerkvist, was named Mebailey in March 1990 for his work on the dynamics and origin of comets. He is the co-author of The Origin of Comets (Pergamon, 1990).