A numerical model of cometary dust environments is used to gain a deeper understanding of the relationship between the brightness ( ) and the dust particle size distribution in the coma. Specifically, the spectral ratio of (425 nm) (900 nm) is modelled for a wide range of parameters and tied to the power-law index. The studied parameters are dust composition, terminal outflow velocity and the dust production rate day–night asymmetry. We find that the spectral ratio of modelled at 425 nm and 900 nm correlates with the power-law index of the particle size distribution. This method could be used to place constraints on the dust size distributions of comets and as a result improve the use of as a proxy for cometary activity. Optically red dust indicates that the scattering is dominated by large particles.
Haslebacher et al. (Tue,) studied this question.