Showing papers by "Rafael Sfair published in 2011"

Gravitational effects of Nix and Hydra in the external region of the Pluto–Charon system

Abstract: Two new companions to the Pluto-Charon binary system have been detected in 2005 by Weaver et al. These small satellites, named Nix and Hydra, are located beyond Charon's orbit. Although they are small when compared to Charon, their gravitational perturbations can decrease the stability of the external region (beyond Charon's orbit). The dynamical structure of this external region is analysed by numerically simulating a sample of particles under the gravitational effects of Pluto, Charon, Nix and Hydra. As expected the effects of Nix and Hydra decrease the external stable region. Agglomerates of particles can survive even after 10 5 orbital periods of the binary in some regions, such as coorbital to Nix and Hydra and between their orbits. We also analysed the effects of hypothetical satellites on the orbital evolution of Nix and Hydra in order to constrain an upper limit size. Some hypothetical satellites can be coorbital to Nix or Hydra without provoking any significant gravitational effects on them.

Small particles in Pluto's environment: effects of the solar radiation pressure

Abstract: Impacts of micrometeoroids on the surfaces of Nix and Hydra can produced dust particles and form a ring around Pluto. However, dissipative forces, such as the solar radiation pressure, can lead the particles into collisions in a very short period of time. In this work we investigate the orbital evolution of escaping ejecta under the effects of the radiation pressure force combined with the gravitational effects of Pluto,Charon, Nix and Hydra. The mass production rate from the surfaces of Nix and Hydra was obtained from analytical models. By comparing the lifetime of the survived particles, derived from our numerical simulations, and the mass of a putative ring mainly formed by the particles released from the surfaces of Nix and Hydra we could estimate the ring normal optical depth. The released particles, encompassing the orbits of Nix and Hydra, temporarily form a 16000 km wide ring. Collisions with the massive bodies, mainly due to the effects of the radiation pressure force, remove about 50% of the $1\mu$m particles in 1 year. A tenuous ring with a normal optical depth of $6 \times 10^{-11}$ can be maintained by the dust particles released from the surfaces of Nix and Hydra.