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arXiv · 2509.21408

Upper Limit on the Non-Gravitational Acceleration and Lower Limits on the Nucleus Mass and Diameter of 3I/ATLAS

Richard Cloete·Abraham Loeb·Peter Vereš
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Abstract

We use astrometric data on 3I/ATLAS compiled by the Minor Planet Center from May 15 to September 23, 2025, and derive an upper limit on any statistically significant deviation from the best-fit gravity-based trajectory. The residuals imply that the non-gravitational acceleration is smaller than $\sim 3 \times 10^{-10}\,{\rm au\,d^{-2}}$. Based on the total mass-loss rate and outflow speed inferred from JWST data on August 6, 2025, we derive lower limits on the mass and diameter of 3I/ATLAS of $3.3 \times 10^{16}\,{\rm g}$ and $5\,{\rm km}$, respectively.

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Richard Cloete, Abraham Loeb, Peter Vereš. 2025-09-24. Upper Limit on the Non-Gravitational Acceleration and Lower Limits on the Nucleus Mass and Diameter of 3I/ATLAS. https://arxiv.org/abs/2509.21408

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