An analytical model for YORP and Yarkovsky effects with a physical thermal lag

Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway e-mail: eirik.mysen@astro.uio.no

Received: 16 November 2007
Accepted: 21 March 2008

Abstract

Asteroids absorb solar radiation, which is later re-emitted. In this paper, an analytic approach for the description of the effects of this thermal emission on the rotation and orbit of an asteroid of unspecified shape is presented. The theory is connected directly to the physics of the problem, and the important results caused by a delayed thermal response of the surface are, therefore, parameterized by the fundamental surface properties of the asteroid. Overall results of previous numerical studies are recovered and an application to the elongated and irregularly-shaped asteroid Eros shows correspondence. The dependency of the derived differential equations on the dynamical variables is explicit and simple. We argue that if the transport of asteroids within the main belt is caused by thermal emission, then there is a preference for the shapes of Earth orbit crossing, regolith-covered asteroids.