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National Repository of Grey Literature 1 records found  Search took 0.00 seconds. 
Rotational dynamics of asteroids affected by thermal emission from topographic features
 Ševeček, Pavel ; Brož, Miroslav (advisor) ; Henych, Tomáš (referee)
Infrared radiation emitted from an asteroid surface causes a torque that can significantly affect rotational state of the asteroid. The influence of small topographic features on this phenomenon, called the YORP effect, hasn't been studied yet in detail. In this work, we show that lateral heat diffusion in surface features of suitable sizes leads to the emergence of a local YORP effect which magnitude is comparable to the YORP effect due to the global shape. We solve a three- dimensional heat diffusion equation in a boulder and its surroundings by the finite element method using the FreeFem++ code. The contribution to the total torque is then inferred from the com- puted temperature distribution. We compare the torque for various boulder shapes and material properties. For an idealized boulder our result is consistent with an existing one-dimensional model. Topographic features may cause a spherical asteroid of radius 1 km on a circular orbit at 2.5 AU to undergo a rotational acceleration of about (2.2 ± 1.1) · 10−9 rad/day2 , which corresponds to the spin-up timescale of the order τ = (32 ± 16) Myr. We estimated a size distribution of boulders based on close-up images of (25143) Itokawa surface. Finally, we realized that topographic features of Itokawa can induce a rotational acceleration of the order 10−7...
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