7 anomalies of the 3I/ATLAS comet: But is it really a comet? Astrophysicist suspects it's something else

Prof. Avi Loeb, a Harvard astrophysicist known for his work on interstellar objects, has highlighted seven key anomalies exhibited by 3I/ATLAS (the third confirmed interstellar object discovered in July 2025).

3I/ATLAS has officially entered our Solar System en route from a distant star system.

These features deviate from expectations for typical natural interstellar visitors like comets or asteroids, prompting Loeb (author of Extraterrestrial: The First Sign of Intelligent Life Beyond Earth) to argue they warrant serious consideration of a technological (or "intelligent") origin.

Below is a summary of these anomalies, drawn from his recent analyses.

Anomaly 1. Size

3I/ATLAS is anomalously large, with an estimated diameter exceeding 5 km (and potentially up to 20 km or more based on albedo assumptions), making it orders of magnitude larger than the previous interstellar objects 1I/'Oumuamua (0.2 km) and 2I/Borisov (1 km).

This rarity is underscored by the infrequency of such large asteroids in our solar system.

Anomaly 2: Jet

The object displays an unusual "anti-tail" or forward-pointing jet (emerging from the leading side rather than the trailing rear), defying standard cometary outgassing models where material is pushed away from the Sun.

Anomaly 3: Composition

Spectroscopic data reveals the presence of nickel in the emissions without accompanying iron, an atypical chemical signature for natural solar system bodies or typical interstellar comets.

Anomaly 4: Polarisation

Observations show anomalous polarisation of light reflected from 3I/ATLAS, inconsistent with the smooth, icy surfaces of known comets and suggesting a more complex, possibly metallic or engineered surface.

Anomaly 5: Inclination

The orbital plane is inclined by only 5 degrees relative to the ecliptic (the plane of the solar system), a fine-tuned alignment that is statistically improbable (0.005% chance) for a random interstellar trajectory and beneficial for accessing inner planets with minimal perturbation.

Anomaly 6: Timing

Discovered on July 1, 2025, at 4.5 AU (astronomical unit) from the Sun, the object's approach timing allows for close passages by Venus, Mars, and Jupiter, with an extraordinarily low probability (<0.005%) for such a "tour" of key planets, resembling a deliberate path rather than random hyperbolic motion.

Anomaly 7: Angular Alignment

The inbound direction of 3I/ATLAS aligns within 9 degrees of the famous "Wow! Signal" (a 1977 radio burst of unknown origin), corresponding to a mere 0.6% likelihood by chance, raising speculative links to potential extraterrestrial transmissions.