As part of our ongoing programs to use adaptive optics (AO) to study asteroids for size, shape, and presence of satellites, we observed asteroid (41) Daphne during its recent close (1.05 AU) opposition. In March 2008, we discovered a small satellite to Daphne at Keck (Conrad et al. 2008, IAUC 8939; Merline et al. 2008, ACM 2008, #8370). Follow up observations at Keck and VLT allowed us to refine the orbit. The unusually short period of the satellite ( 1.1 day) and the estimated size (239x183x153 km) from our observations lead to a density near 2.0 g/cc. This is significantly higher than most other large C-types with densities determined from presence of a moon (Merline et al. 2002, Asteroids III, 289). Because of this surprising density, and because we expect to derive an exceptionally accurate volume from our data, we are placing special emphasis on our size and shape determinations. One of the peculiarities is that this object is highly irregular in shape. We demonstrate several methods of determining the volume, including triaxial ellipsoid fits, detailed shape modeling, and improving estimates by using existing lightcurve information (e.g., from Kaasalainen et al.).
AAS/Division for Planetary Sciences Meeting Abstracts #40
- Pub Date:
- September 2008