Comet dust as a size distribution of irregularly shaped, compact particles

A systematic study aimed at searching the physical parameters characterizing cometary dust grains that best fit the observations has been conducted. Although it has long been assumed that the cometary dust is mainly composed of strongly absorbing aggregates having monomers of about a tenth of a micrometer in size, all the properties shown by cometary dust particles, particularly those related to phase angle variation of intensity and degree of linear polarization, and their color dependences, have not yet been simultaneously reproduced to date. In this paper we demonstrate that size distributions of moderately absorbing, irregularly shaped, and compact particles of various degree in shape complexity, constitute an alternative approach to explain the observed properties of cometary dust. Aggregate structures produce a much larger degree of linear polarization for incident unpolarized light at side angles than particles having a more compact structure when compared with polarimetric observations of comets.