COSINE (Cometary Object Study Investigating their Nature and Evolution) II: Colors and Sizes of Comet Nuclei
Abstract
Comet nuclei preserve a record of planetesimal formation, but their sizes are difficult to measure because the nucleus is usually blended with its coma. We present a catalog of nucleus sizes for 523 comets (235 long-period and 288 short-period comets; LPCs and SPCs) from the 14.5-year WISE/NEOWISE archive, supplemented by Spitzer photometry. A coma-nucleus decomposition of the radial profiles yields conservative upper limits for all 523 comets and diameters with uncertainties for 301 (107 LPCs and 194 SPCs), with median diameters of 5.3 and 2.5 km, respectively. Nucleus colors across the four WISE bands follow the heliocentric trend expected from the transition between reflected and thermal emission, with no measurable difference between the two dynamical classes. The cumulative size-frequency distribution of the SPCs has a slope of γ= 1.45−0.13+0.15 (68% confidence interval) over D = 2--15 km, steepening to 2.05−0.38+0.47 for the perihelion q < 2 au subset. The LPC distribution is smoothly concave down: a broken power law places a break near 35 km, with slopes of 0.92−0.12+0.13 below and 3.68−1.24+1.96 above, while the q < 2 au subset gives 1.39−0.28+0.35 over D = 4--20 km. All distributions flatten below the fitted ranges and level off near 1 km. We discuss the implications of our results and their connection with models of the destabilized trans-Neptunian population.
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BibTeX
@misc{kwon2026cosine,
title = {{COSINE (Cometary Object Study Investigating their Nature and Evolution) II: Colors and Sizes of Comet Nuclei}},
author = {Yuna G. Kwon and Dar W. Dahlen and Joseph R. Masiero and Yanga R. Fernández and Adeline Gicquel and James M. Bauer and Yoonyoung Kim and Frank Masci and Amy K. Mainzer},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.32110},
eprint = {2609.32110},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.32110},
}
RIS
TY - UNPB
TI - COSINE (Cometary Object Study Investigating their Nature and Evolution) II: Colors and Sizes of Comet Nuclei
AU - Yuna G. Kwon
AU - Dar W. Dahlen
AU - Joseph R. Masiero
AU - Yanga R. Fernández
AU - Adeline Gicquel
AU - James M. Bauer
AU - Yoonyoung Kim
AU - Frank Masci
AU - Amy K. Mainzer
PY - 2026
DA - 2026/09/26
PB - arXiv
DO - 10.48550/arxiv.2609.32110
UR - https://arxiv.org/abs/2609.32110
AB - Comet nuclei preserve a record of planetesimal formation, but their sizes are difficult to measure because the nucleus is usually blended with its coma. We present a catalog of nucleus sizes for 523 comets (235 long-period and 288 short-period comets; LPCs and SPCs) from the 14.5-year WISE/NEOWISE archive, supplemented by Spitzer photometry. A coma-nucleus decomposition of the radial profiles yields conservative upper limits for all 523 comets and diameters with uncertainties for 301 (107 LPCs and 194 SPCs), with median diameters of 5.3 and 2.5 km, respectively. Nucleus colors across the four WISE bands follow the heliocentric trend expected from the transition between reflected and thermal emission, with no measurable difference between the two dynamical classes. The cumulative size-frequency distribution of the SPCs has a slope of γ= 1.45_−0.13^+0.15 (68% confidence interval) over D = 2--15 km, steepening to 2.05_−0.38^+0.47 for the perihelion q < 2 au subset. The LPC distribution is smoothly concave down: a broken power law places a break near 35 km, with slopes of 0.92_−0.12^+0.13 below and 3.68_−1.24^+1.96 above, while the q < 2 au subset gives 1.39_−0.28^+0.35 over D = 4--20 km. All distributions flatten below the fitted ranges and level off near 1 km. We discuss the implications of our results and their connection with models of the destabilized trans-Neptunian population.
ER -