Asteroid rotation I. Tabulation and analysis of rates, pole positions and shapes
Abstract
Data are presented for the 182 asteroids whose rotational properties are available in the literature. Plots are provided for the asteroid rotational frequency f and lightcurve amplitude ∆m versus asteroid size; the latter is determined using standard methods if data are available but otherwise is estimated from asteroid albedos, selected depending on taxonomic type or orbital position. A linear leastsquares fit to all the data shows that f increases with decreasing size, confirming McAdoo and Burns' (1973) result; this is demonstrated to be primarily caused by relatively more small nonC than C asteroids in our sample, coupled with a slower mean rotation rate for C asteroids ( P ≈ 11 hr) than nonC asteroids ( P ≈ 9 hr). In terms of the collisional theory of Harris (1979a), this means that the C's are less dense than the other minor planets. Any slight tendency for smaller asteroids to spin faster, even within a taxonomic type, could be due to selection effects; our data are not extensive enough to determine whether the very smallest (⪅ 10km diameter) spin especially fast. The minor planets of our survey become more irregular at smaller sizes, disputing the conclusions of Bowell (1977b), Degewij (1977), and Degewij et al. (1978), based on other, perhaps more complete, data; selection effects may account for this disagreement. Shapes do not appear to depend on taxonomic type. The dispersion of asteroid rotation rates from the mean is found to be in excellent agreement with a threedimensional Maxwellian distribution, such as would be developed in a collisionally evolved system. The rotation axes, therefore, appear to be randomly oriented in space. Rotation pole positions are also tabulated and calculated to likely be constant in space over the extent of past observation. Observers are encouraged to measure the rotational properties of faint objects and asteroids of unusual taxonomic types, and to carry out longtime studies of asteroids which over short periods do not seem to vary.
 Publication:

Icarus
 Pub Date:
 October 1979
 DOI:
 10.1016/00191035(79)900587
 Bibcode:
 1979Icar...40..115H
 Keywords:

 Angular Velocity;
 Asteroids;
 Astronomical Photometry;
 Planetary Rotation;
 Astronomical Models;
 Light Curve;
 Shapes;
 Size (Dimensions);
 Lunar and Planetary Exploration