What the Seven-Hour Rotation Might Mean
Before perihelion, brightness data suggested a longer periodicity of roughly 16 to 17 hours. Loeb argues that the discrepancy does not necessarily indicate that the object sped up, but instead that perihelion may have activated additional jets or source regions.
If only one rotational pole was illuminated before perihelion, and both poles became active afterward, the brightness cycle could effectively double in frequency without a change in the underlying spin rate. In that scenario, the seven-hour signal reflects jet geometry rather than a fundamental change in rotation.
Crucially, Loeb reports that the jet precession period before perihelion and after perihelion are broadly consistent, reinforcing the idea that 3I/ATLAS retained its rotational stability despite intense solar heating.
As 3I/ATLAS approaches near-perfect opposition on January 22, 2026, Loeb notes that the viewing geometry will change again, with the anti-sunward jet fading from view and the sunward anti-tail pointing almost directly toward Earth. That alignment could provide another test of whether jet-driven modulation — rather than nucleus reflection — truly governs the object’s observed variability.
For now, the reported seven-hour rotation period adds another intriguing piece to the puzzle of how interstellar objects behave when they pass through our solar system — and how much they can reveal about conditions far beyond it.
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