ORBITAL IDENTIFICATION FOR ASTEROID 152563 (1992 BF) THROUGH THE YARKOVSKY EFFECT

Abstract

Often a newly discovered near-Earth asteroid is linked to old observations of a formerly lost object. This orbital identification is done using a standard dynamical model that accounts for gravitational perturbations from planets and relativistic effects. Here we report the first case where such an identification requires consideration of the Yarkovsky effect, a tiny non-gravitational perturbation due to the recoil of thermal radiation from the body. Moreover, this implies that the Yarkovsky force is revealed in the orbital motion of the body, asteroid 152563 (1992 BF), only the second case so far. Orbital fits indicate a drift in the orbital semi-major axis of –(10.7 ± 0.7) × 10–4 AU Myr–1, which we ascribe to Yarkovsky forces. This yields a correlated constraint of physical parameters such as the obliquity, rotation rate, surface thermal inertial, and bulk density. The magnitude and direction of drift point to an obliquity in excess of 120°. Observations taken during 2011 and subsequent close encounters with the Earth might help establish rotation parameters and thereby constrain thermal inertia of 1992 BF, thus making the Yarkovsky strength a measure of this asteroid's bulk density.