Polarimetric Behaviour of (3200) Phaethon: New Observations with Implications for Surface Heterogeneity
Abstract
The near-Earth asteroid (3200) Phaethon exhibits unusually high linear polarisation at large phase angles. Previous observations revealed a significant difference between apparitions: measurements obtained in 2016 showed a polarisation up to ∼10 percentage points higher than those obtained in 2017 at comparable phase angles. The distinct surface regions and viewing geometries sampled during the two apparitions have been suggested as possible explanations for this difference. Here, we present new R-band polarimetric observations obtained with the Nordic Optical Telescope, covering phase angles 32∘<α<103∘. The 2019 measurements show polarisation intermediate between higher and lower values measured in 2016 and 2017, respectively. Using a recent shape model, we calculate the distribution of reflected flux across the surface during the three individual apparitions and find that the 2019 observations sample the surface more similarly to 2016 than to 2017. We explore several possible explanations for the different polarisation behaviours, including differences in regolith grain size, related surface albedo, and observing geometry. While the available observations do not allow these effects to be uniquely disentangled, our results and analysis suggest that surface heterogeneity is the most plausible underlying cause, with viewing geometry potentially contributing to the observed polarimetric differences.
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BibTeX
@misc{gray2026polarimetric,
title = {{Polarimetric Behaviour of (3200) Phaethon: New Observations with Implications for Surface Heterogeneity}},
author = {Zuri Gray and Mikko Vuori and Eric MacLennan and Mikael Granvik and Karri Muinonen and Antti Penttilä and Mikael Turkki},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.09110},
eprint = {2610.09110},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.09110},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Polarimetric Behaviour of (3200) Phaethon: New Observations with Implications for Surface Heterogeneity
AU - Zuri Gray
AU - Mikko Vuori
AU - Eric MacLennan
AU - Mikael Granvik
AU - Karri Muinonen
AU - Antti Penttilä
AU - Mikael Turkki
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.09110
UR - https://arxiv.org/abs/2610.09110
AB - The near-Earth asteroid (3200) Phaethon exhibits unusually high linear polarisation at large phase angles. Previous observations revealed a significant difference between apparitions: measurements obtained in 2016 showed a polarisation up to ∼10 percentage points higher than those obtained in 2017 at comparable phase angles. The distinct surface regions and viewing geometries sampled during the two apparitions have been suggested as possible explanations for this difference. Here, we present new R-band polarimetric observations obtained with the Nordic Optical Telescope, covering phase angles 32^∘<α<103^∘. The 2019 measurements show polarisation intermediate between higher and lower values measured in 2016 and 2017, respectively. Using a recent shape model, we calculate the distribution of reflected flux across the surface during the three individual apparitions and find that the 2019 observations sample the surface more similarly to 2016 than to 2017. We explore several possible explanations for the different polarisation behaviours, including differences in regolith grain size, related surface albedo, and observing geometry. While the available observations do not allow these effects to be uniquely disentangled, our results and analysis suggest that surface heterogeneity is the most plausible underlying cause, with viewing geometry potentially contributing to the observed polarimetric differences.
ER -