Obliquity dependence of the tangential YORP

¹ Institute of Astronomy, Charles University, Prague, V Holešovičkách 2, 18000 Prague 8, Czech Republic
e-mail: sevecek@sirrah.troja.mff.cuni.cz
² Department of Aerospace Engineering Sciences, University of Colorado at Boulder, 429 UCB, Boulder, CO 80309, USA
³ Kharkiv National University, 4 Svobody Sq., 61022 Kharkiv, Ukraine
⁴ Institute of Astronomy, Kharkiv National University, 35 Sumska Str., 61022 Kharkiv, Ukraine

Received: 19 April 2016
Accepted: 20 May 2016

Abstract

Context. The tangential Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect is a thermophysical effect that can alter the rotation rate of asteroids and is distinct from the so-called normal YORP effect, but to date has only been studied for asteroids with zero obliquity.

Aims. We aim to study the tangential YORP force produced by spherical boulders on the surface of an asteroid with an arbitrary obliquity.

Methods. A finite element method is used to simulate heat conductivity inside a boulder, to find the recoil force experienced by it. Then an ellipsoidal asteroid uniformly covered by these types of boulders is considered and the torque is numerically integrated over its surface.

Results. Tangential YORP is found to operate on non-zero obliquities and decreases by a factor of two for increasing obliquity.