Detailed study of the Yarkovsky effect on asteroids and solar system implications

Abstract

The Yarkovsky effect is a change in a body's orbit caused by its reaction to the momentum carried away by the thermal photons that it emits. This effect may play a key role in the orbital evolution of asteroids and near-Earth objects. To evaluate the Yarkovsky acceleration under a wide range of conditions, I have developed a three-dimensional finite-difference solution to the heat equation. This approach employs neither the linearized boundary conditions, the plane-parallel heat flow approximation, nor the assumption of fast rotation used in earlier approaches (Rubincam, 1998; Vokrouhlickỳ and Farinella, 1998). Thus it can be used to explore a wide range of orbital elements and physical properties that had not been previously accessible. I use the finite-difference approach to compute Yarkovsky perturbations for homogeneous, spherical stony bodies with 1-, 10- and 100-m diameters. For a 1-m scale body rotating with a 5-h period, the semimajor axis can change as much as 1 AU in 1 Myr and the eccentricity can change as much as 0.1 in 1 Myr. These rates are much faster than any found previously because those treatments were not valid for very eccentric orbits. For rotation periods expected to be more typical of such small bodies, these rates would be considerably slower. Nevertheless, there is no data concerning rotation rates for small bodies so these fast rates may be relevant. Yarkovsky drift rates are computed for models of specific near-Earth asteroids, demonstrating that the shape of a body is important in computing its precise Yarkovsky effect. Such calculations may be useful for assessing observable Yarkovsky perturbations and in predicting and mitigating NEA hazards. The approach presented in this dissertation is the only current one with the potential to rigorously treat bodies with arbitrary shapes.