3I/ATLAS (C/2019 Y4) - Photometric Anomaly 2025

This dataset documents the photometric brightening anomaly of 3I/ATLAS (C/2019 Y4) observed between July and October 2025.Raw photometric observations were extracted directly from the Minor Planet Center file I3.txt and processed using the included open-source Python script print_summary.py.The analysis reveals a sustained increase in brightness from V ≈ 17.3 mag to V ≈ 13.1 mag (Δm ≈ 4.2 mag, ≈ ×47 flux), far exceeding the variation expected from geometric factors alone. The anomaly likely represents post-conjunction reactivation or outgassing of volatile material.All magnitudes are direct MPC values (no interpolation), ensuring full reproducibility. All files are cryptographically sealed with SHA-256 checksums and timestamp-anchored in the Bitcoin blockchain using OpenTimestamps.