2025/12/14 by M. Serra-Ricart, J. Licandro, Serra-Ricart, M. +3 · 4 voices · 2 citations
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Planetary Science and Exploration #astro-ph.EP #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.48550/arxiv.2512.12819
We present observations of the detection of a faint high-latitude jet in the inner coma of comet 3I/ATLAS that coincides with the broad plume detected in visible images along PA 280 ± 10∘. A detailed analysis shows that the jet was clearly detected on seven nights (2025, August~3, 5, 18, 19, 21, 24, and~29). The jet maintains an almost, though not perfectly, constant position angle (PA) throughout these epochs. High-precision PA measurements at a projected distance of 6000~km from the cometary optocenter reveal a periodic modulation centered at ~ 280 degrees, consistent with a high-latitude jet undergoing precessional motion around the sky-projected spin axis of the nucleus. This is the first periodic jet-angle modulation detected in an interstellar comet. The derived periodicity of 7.74 ± 0.35 h may imply a nucleus rotation period of Prot = 15.48 ± 0.70 h if the jet originates from a single active source near one of the poles. This value is slightly shorter than the period of Prot = 16.79 ± 0.23 h derived from the photometric time series. From the measured PA range, the sky-projected orientation of the spin axis is derived as PA = 280.7 ± 0.2∘