Polarimetric study of comets from Mt. Abu observatory

Abstract

The sunlight is scattered by the dust grains present in the coma and tail of comets which makes it visible. The scattered sunlight is characteristically polarized with degree of polarization generally depending upon the phase angle, wavelength of the incident light, shape and size distribution of the scattering particles and refractive indices of the particles. High precision photopolarimetric observations at several wavebands and phase angles were made on several bright comets during the last decade using the facilities at Mt. Abu observatory with the aim to study the characteristics of the dust grains in the comets. All these comets were bright comets and found to belong to high polarization class of comets. At low phase angles comets show signi cant negative polarization indicating the grains to be regolith consisting of monomers of sub micron size