Author/Authors :
Descamps، نويسنده , , P. and Marchis، نويسنده , , F. and Berthier، نويسنده , , J. and Emery، نويسنده , , J.P. and Duchêne، نويسنده , , Henry G. and de Pater، نويسنده , , I. and Wong، نويسنده , , M.H and Lim، نويسنده , , L. and Hammel، نويسنده , , H.B. and Vachier، نويسنده , , F. and Wiggins، نويسنده , , P. and Teng-Chuen-Yu، نويسنده , , J.-P. and Peyrot، نويسنده , , A. and Pollock، نويسنده , , J. and Assafin، نويسنده , , M. and Vieira-M، نويسنده ,
Abstract :
To take full advantage of the September 2008 opposition passage of the M-type Asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO) imaging with the W.M. Keck II telescope to capture unprecedented high resolution images of this unusual asteroid. Our AO observations with the W.M. Keck II telescope, combined with Spitzer/IRS spectroscopic observations and past stellar occultations, confirm the value of its IRAS radiometric radius of 67.5 km as well as its dog-bone shape suggested by earlier radar observations. Our Keck AO observations revealed the presence of two small satellites in orbit about Kleopatra (see Marchis, F. et al. [2008a]. (3749) Balam. In: Green, D.W.E. (Ed.), IAU Circ. 8928; Marchis, F., Descamps, P., Berthier, J., Emery, J.P. [2008b]. S/2008 ((216)) 1 and S/2008 ((216)) 2. In: Green, D.W.E. (Ed.), IAU Circ. 8980). Accurate measurements of the satellite orbits over a full month enabled us to determine the total mass of the system to be 4.64 ± 0.02 × 1018 kg. This translates into a bulk density of 3.6 ± 0.4 g/cm3, which implies a macroscopic porosity for Kleopatra of ∼30–50%, typical of a rubble-pile asteroid. From these physical characteristics we measured its specific angular momentum, very close to that of a spinning equilibrium dumbbell.
Keywords :
Orbit Determination , Asteroids , Photometry , Satellites of asteroids , adaptive optics
