Rare Near-Opposition Alignment of 3I/ATLAS on 22 January, 2026

Mauro Barbieri; Abraham Loeb

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arXiv · 2601.08624

Rare Near-Opposition Alignment of 3I/ATLAS on 22 January, 2026

Mauro Barbieri·Abraham Loeb

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Abstract

We point out that on 22 January 2026, the interstellar object 3I/ATLAS will align to within an exceptionally small angle, alpha= 0.69 degrees, with the Earth-Sun axis. This rare alignment provides unique circumstances for measuring the opposition surge and polarimetric properties of interstellar cometary dust. We characterize the alignment geometry, outline key scientific opportunities, and define the observational requirements for data collection. Observations before and after the alignment time offer an unprecedented opportunity which may not repeat for decades, for characterizing the albedo, structure, and composition of interstellar matter.

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Mauro Barbieri, Abraham Loeb. 2026-01-13. Rare Near-Opposition Alignment of 3I/ATLAS on 22 January, 2026. https://arxiv.org/abs/2601.08624

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