The effect of density inhomogeneity on the YORP effect for a given shape
model is investigated. A density inhomogeneity will cause an offset between the
center of figure and the center of mass and a re-orientation of the principal
axes away from those associated with the shape alone. Both of these effects can
alter the predicted YORP rate of change in angular velocity and obliquity. We
apply these corrections to the Itokawa shape model and find that its YORP
angular velocity rate is sensitive to offsets between its center of mass and
center of figure, with a shift on the order of 10 meters being able to change
the sign of the YORP effect for that asteroid. Given the non-detection of YORP
for Itokawa as of 2008, this can shed light on the density distribution within
that body. The theory supports a shift of the asteroid center of mass towards
Itokawa's neck region, where there is an accumulation of finer gravels.
Detection of the YORP effect for Itokawa should provide some strong constraints
on its density distribution. This theory could also be applied to asteroids
visited by future spacecraft to constrain density inhomogeneities.Comment: 23 pages, 3 figure