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Nucleus rotation period of 3I/ATLAS is unconstrained by TESS

Determine the rotation period of the nucleus of the interstellar object 3I/ATLAS using observations or analyses that overcome the noise-dominated Transiting Exoplanet Survey Satellite (TESS) Sector 92 light curves, which exhibit a ∼28-hour peak consistent with background pixels and therefore do not constrain the nucleus rotation period.

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Background

The authors extracted a 20-day light curve of 3I/ATLAS from TESS Full-Frame Images in Sector 92 and analyzed it with Lomb–Scargle periodograms to search for periodicity between 1 and 70 hours. Both camera/CCD datasets showed a peak near 28 hours, initially suggesting a possible rotational signature.

A comparison to nearby background pixels revealed similar peaks, indicating that the signal was dominated by instrumental/systematic noise. Consequently, the authors concluded that the TESS data cannot constrain the rotation period of the 3I/ATLAS nucleus, likely due to coma contributions, nucleus size uncertainties, or insufficient TESS sensitivity at these magnitudes.

References

We find that the light curve and resulting periodogram are dominated by noise and therefore we cannot constrain the rotation period of the nucleus.

— Precovery Observations of 3I/ATLAS from TESS Suggests Possible Distant Activity (2507.21967 - Feinstein et al., 29 Jul 2025) in Figure 6 caption; Section 3.1 (Photometric Light Curve)