On the Slow Rotation of Asteroids

✍ Scribed by Alan W. Harris

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 156 KB
• Volume: 156
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.2001.6778

✦ Synopsis

Asteroids with very slow rotation rates, up to 100 times slower than the mean for ordinary asteroids, are clearly a statistically distinct population from the rest. The cause of such slow rotation has remained a mystery since the discovery of the population about 20 years ago. The expected distribution of slow rotations for threedimensional rotation vectors f if uniform near the origin (e.g., a three-dimensional Maxwellian distribution) would be N (< f ) ∝ f 3 , where f is the rotation frequency (inverse period of rotation) and N (< f ) is the cumulative number of asteroids with spin rate less than f. In this paper I show that the statistics of the slow-rotation population as currently known is well fit as a uniform distribution of the one-dimensional parameter f, that is N (< f ) ∝ f. I offer as a possible explanation for slow rotations that they result from disintegration of high mass ratio (∼1 : 5) binaries through the rapid transfer of rotational energy of the primary into the orbit of the secondary due to the irregular gravity field of the primary. A troubling aspect of this hypothesis is that it would seem to predict a distribution of residual spins of the approximate form N (< f ) ∝ f 2 , which does not fit the available data.