Jet Precession and an Unusual Alignment
Loeb notes that the jet does not remain fixed in direction but instead appears to precess around the rotation axis, producing both the observed jet wobble and the brightness variations. The average jet orientation points near 270 degrees on the sky, while the Sun–3I/ATLAS direction lies near 290 degrees.
This implies that the object’s rotation axis is aligned with the Sun–object axis to within roughly 10–20 degrees — an alignment Loeb describes as statistically unlikely to occur at random for an object that formed in interstellar space.
That alignment matters because earlier Hubble observations showed that less than one percent of the observed light from 3I/ATLAS comes from the solid nucleus. Most of the brightness originates in the surrounding coma. As a result, the seven-hour brightness cycle is not thought to reflect sunlight bouncing off a rotating solid body, but rather the changing geometry of dust and gas jets.
In Loeb’s interpretation, the rotating nucleus drives jets that sweep through space like a rotating sprinkler, periodically thickening or thinning the dust along Earth’s line of sight. This produces a rhythmic, jet-driven brightness signal — what he has previously described as a kind of “heartbeat” variability.
