Distribution of spin axes and shape elongations of main-belt asteroids
Abstract
Photometric data that are sparse in time (typically few measurements per night over ~15 years) are a potential source of information about shapes and rotational states of asteroids. However, currently available data are usually not accurate enough to derive a unique sidereal rotation period and corresponding shape model by the lightcurve inversion method. To fully utilize sparse-in-time data, we have developed a new simplified model that provides an approximate solution for the orientation of the spin axis (λ, β) and ratios of axes of the ellipsoid, a/b, b/c (asteroids are modelled as geometrically scattering triaxial ellipsoids). The observed values of mean brightness (over one apparition) and the dispersion of brightness are compared with values computed from the model parameters (λ, β, a, b, setting c=1) which are optimized to get the best agreement. The model was applied on the data from Lowell photometric database. We found that the distribution of pole ecliptic longitude λ is nonuniform and that this nonuniformity is larger for asteroids with low inclination of their orbits. The second main result is that small asteroids (D<25 km) are on average more elongated (a/b ~ 1.6) than the large ones (for D>50 km the mean value of a/b is 1.3).
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #48
- Pub Date:
- October 2016
- Bibcode:
- 2016DPS....4832607C