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

TL;DR

This paper discusses a rare astronomical alignment of interstellar object 3I/ATLAS with Earth-Sun axis on 22 January 2026, offering unique scientific opportunities for studying interstellar dust properties.

Contribution

It characterizes the alignment geometry and outlines observational strategies to study interstellar dust during this rare event.

Findings

Alignment angle of 0.69 degrees identified

Opportunities for measuring opposition surge and polarization

Potential to analyze interstellar dust composition

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.