The radial surface brightness distribution shows that the disk density peaks at a distance of 40 AU from the star corresponding to the edge of the planetary zone in our solar system. The normal optical thickness found is more than 100 times larger than in the case of the Pic disk. Simultaneously, the presence of sub-micronic particles sizes, well below the radiation pressure cut-off in sizes, suggests that huge quantities of very small particles are produced continuously by evaporation or collisions of planetesimals. We are probably witnessing a analogue of the young Kuiper belt with planetesimals undergoing violent agitation. If the dust particles are the result of collisions, a high rate is required to produce the observed disk. This implies that gravitational perturbations occur frequently in this disk, maybe because of giant planets. If the disk is replenished by planetesimal evaporation as suggested by Lecavelier des Etangs (1998) in the case of the Pic disk, 109 planetesimals (40 km size) whose orbits were recently perturbed by planet migration are required to maintain the disk. Some of them which orbits are gravitationally perturbed might be the origin of the casual redshifted absorption profiles observed in some of the spectra of HD 100546 (Grady et al. 1997), a phenomenon highly similar to what is observed in the system of Pictoris (Lagrange-Henry et al. 1987, Beust et al. 1996).
© European Southern Observatory (ESO) 2000
Online publication: September 5, 2000