A&A 471, 345-353 (2007)
DOI: 10.1051/0004-6361:20077313
Radiation-induced torques on spheroids
S. Breiter1, H. Michalska1, D. Vokrouhlický2, 3, and W. Borczyk11 Astronomical Observatory, A. Mickiewicz University, Sloneczna 36, 60-286 Poznan, Poland
e-mail: breiter@amu.edu.pl
2 Institute of Astronomy, Charles University, V Holesovickách 2, 18000 Prague, Czech Republic
e-mail: vokrouhl@mbox.cesnet.cz
3 Department of Space Studies, Southwest Research Institute, 1050 Walnut St., Boulder, CO 80302, USA
(Received 16 February 2007 / Accepted 24 May 2007)
Abstract
Radiation-induced torques on ellipsoids of revolution are discussed.
Exact formulae for the thermal YORP torques are given in terms of elliptic integrals.
It is demonstrated that in the absence of thermal inertia, the average values of
dynamically significant projections of these torques are zero if a spheroid rotates
around the axis of maximum inertia and if there are no resonances between rotation
and orbital motion. The thermal lag leads to a systematic drift in the obliquity, but
it does not affect the rotation period. The direct radiation pressure torques on spheroids are shown to be zero.
Key words: methods: analytical -- celestial mechanics -- minor planets, asteroids
© ESO 2007

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