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The Interstellar Comet Kept Its Color Through Perihelion
Fourteen optical epochs and near-infrared follow-up trace 3I/ATLAS across ten months, finding persistent dust but no robust water-ice absorption.
Summary
Fourteen optical epochs and near-infrared follow-up trace 3I/ATLAS across ten months, finding persistent dust but no robust water-ice absorption.
Keck and Gemini observations followed interstellar comet 3I/ATLAS from July 2025 through May 2026 with optical imaging, spectroscopy and near-infrared measurements. The team reports no significant mean optical-color change across perihelion, a steeper decline in phase-corrected red-band activity outbound than inbound and extended dust persisting into February. Gas ratios evolved, while the near-infrared spectra did not show water-ice absorption robust to the tested continuum and calibration choices. Dust-loss and surface-layer estimates depend on adopted grain and nucleus assumptions. The campaign is a detailed observational record, not proof of the comet's full composition, and is the text-only report beneath the feature.
Why it matters
Fourteen optical epochs and near-infrared follow-up trace 3I/ATLAS across ten months, finding persistent dust but no robust water-ice absorption.
Limits and context
- Gas ratios evolved, while the near-infrared spectra did not show water-ice absorption robust to the tested continuum and calibration choices.
- The campaign is a detailed observational record, not proof of the comet's full composition, and is the text-only report beneath the feature.
Key claims
Fourteen optical epochs and near-infrared follow-up trace 3I/ATLAS across ten months, finding persistent dust but no robust water-ice absorption.
Qualification: Gas ratios evolved, while the near-infrared spectra did not show water-ice absorption robust to the tested continuum and calibration choices.
Evidence: source-2026-10-26-016
Sources
- arXiv preprint 2610.32972, original v1arXiv · primary research
Corrections
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