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Astron. Astrophys. 350, 1079-1084 (1999)

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An improved model of the seasonal Yarkovsky force for regolith-covered asteroid fragments

David Vokrouhlický and Miroslav Bro

Institute of Astronomy, Charles University, V Holeovikách 2, 180 00 Prague 8, Czech Republic (vokrouhl@mbox.cesnet.cz; mira@sirrah.troja.mff.cuni.cz)

Received 13 April 1999 / Accepted 27 August 1999

Abstract

We derive a new analytical solution for the seasonal Yarkovsky effect, the mean-motion frequency mode of the recoil force due to reradiated sunlight, on a spherical asteroid fragment. The body is assumed to have a thin low-conductivity (regolith-like) surface layer, covering a much more thermally conductive core. If the penetration depth of the seasonal thermal wave in the low-conductivity surface material is larger than the regolith's geometrical thickness, the previous simplified solution assuming a homogeneous interior of the body might lead to wrong estimates on the intensity of the perturbing force. Our approach removes this problem and the results indicate: (i) an increased seasonal mobility of 10-m sized and larger fragments with an insulating surface layer, and (ii) a decreased seasonal mobility of meter-sized fragments with the same structure. These results may affect the accuracy of simulations of meteorite and NEA transport to the Earth, as well as the dynamical evolution of some real small asteroids (e.g. 1566 Icarus).

Key words: celestial mechanics, stellar dynamics – minor planets, asteroids

Send offprint requests to: D. Vokrouhlický

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© European Southern Observatory (ESO) 1999

Online publication: October 14, 1999
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