Monitoring the negative polarization in Comet 29P/Schwassmann–Wachmann during quiescence

Abstract

During five nights between February 3 and 10, 2021, we monitored the degree of linear polarization in Comet 29P/Schwassmann–Wachmann with the broadband R filter. It is the first polarimetric investigation of this comet measured during a period of quiescent activity. We found a nearly constant negative polarization PQ ≈ −2.1% at α ≈ 9.5° that is somewhat stronger than in other comets on average; however, it appears similar to that of Comet 67P/Churyumov–Gerasimenko. Modeling the polarization in Comet 29P/Schwassmann–Wachmann suggests its coma consists of at least two components, whose chemical composition and size distribution appear similar to that of other comets. Further polarimetric measurements are necessary in order to infer the shape of its branch of negative polarization and, hence, better constrain the microphysical properties of its dust.