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arXiv · 2610.34558

Partial Fragmentation of Comet C/2025 K1 (ATLAS)

Jane Luu·David Jewitt
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Abstract

We present time-series observations of the long period comet C/2025 K1 (ATLAS) obtained in 2025-2026, bracketing the comet's fragmentation in early November 2025. We show that a simple radiation pressure model can explain many of the comet's properties: the rapid fading after fragmentation, the increasing mean particle size in the projected photometry aperture, and the time dependence of the surface brightness profile. Small dust particles ($\lesssim 100 μ$m) dominate the coma, with average dust velocity $\sim$ a few $\times$ 1 meter s$^{-1}$. The nucleus radius is estimated at $\sim$0.5 km and the dust properties are consistent with, but do not prove, an origin in nucleus rotational breakup, followed by being swept down the tail by radiation pressure.

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Jane Luu, David Jewitt. 2026-10-25. Partial Fragmentation of Comet C/2025 K1 (ATLAS). https://arxiv.org/abs/2610.34558

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