paper

A comprehensive study of comet 67P/Churyumov-Gerasimenko in the 2021/2022 apparition. II. Colorimetry, polarimetry, modeling

arXiv:2607.20038 · doi:10.1016/j.icarus.2025.116799

Abstract

This paper presents the second part of our multi-technique observational study of comet 67P during its 2021-2022 apparition. While the first paper focused on photometry and spectroscopy, here we investigate the dust color and linear polarization of the coma. Imaging in the g-sdss and r-sdss filters was obtained with the 6-m BTA SAO Telescope, and aperture polarimetry was performed with the 2.6-m Shajn Telescope (CrAO) and the 2-m RCC Telescope. Observations at phase angles of 47.9 deg (6 October 2021) and 10.5 deg (6 February 2022) show negative polarization of about 0.5-2.5% at 10.5 deg and positive polarization of about 11% at 47.9 deg. The dust color was red, reaching about 0.8 mag near the nucleus and in the tail, and decreasing to about 0.2 mag in the coma and jet within 20,000 km of the nucleus. Spatial maps reveal a gradual decrease in color index and a corresponding increase in polarization with distance from the nucleus. Numerical modeling using ballistic particle-cluster aggregates composed of equal fractions of silicates and organics indicates that the coma is dominated by particles larger than 10 micrometers, while local polarization enhancements are consistent with regions containing smaller (1-10 micrometer) grains. Combining our aperture measurements with published data from four previous apparitions confirms that comet 67P belongs to the high-polarization class. The unusually high positive polarization observed during the 2021/22 apparition, together with the relatively isotropic coma morphology, suggests that the dust properties may have changed after the 2015/16 apparition.

15 pages, 11 figures

References in corpus (13)

Cited by in corpus (1)