Harvard astrophysicist questions the origin of 3I/Atlas as a possible alien spacecraft in scientific debate

Astrophysicist Avi Loeb, professor of Harvard, analyzed the interstellar object 3I/Atlas in a recent interview with the program natural rock or signs of advanced technology.

The detection of 3I/Atlas occurred on July 1, 2025, by the ATLAS system in Chile, and its hyperbolic trajectory confirms origin outside of Sistema Solar.

Loeb highlights anomalies observed by telescopes such as Hubble and James Webb, including non-gravitational acceleration and gas jets.

• Size estimated at up to 20 km, larger than most interstellar comets.
• Initial absence of visible coma, unusual for icy objects.
• Trajectory aligned with the ecliptic plane, with passages close to Vênus, Marte and Júpiter.

These data, according to Loeb, increase the probability of artificial origin to around 40%, although most scientists defend natural explanations.

Unusual trajectory of 3I/Atlas sparks speculation

Avi Essa proximity, called perihelion, occurred 1.4 astronomical units from Sol, without risk for Terra.

NASA observations reveal that the object has lost significant mass, with jets of gas detected after perihelion.

Telescopic observations reveal jets and emissions

Telescopes like Hubble captured images of 3I/Atlas in July 2025, showing a coma of dust and gas.

The ultraviolet emission, measured by the MAVEN probe at Marte, indicates a composition rich in carbon dioxide, with a ratio of CO2 ice to water of 8:1.

Loeb points out that seven jets, visible in photos from November 2025, extend as far as 1.8 million kilometers, defying models of solar comets.

These structures, directed towards Sol, form a frontal “anti-tail”, a rare phenomenon in natural objects.

Debate over origin divides scientific community

NASA classified 3I/Atlas as a natural comet at a conference on November 19, 2025, at Washington, based on spectra showing metals such as nickel and iron.

Experts like Jacqueline McCleary, from Northeastern University, attribute the early shine to the unique composition, without the need for extraterrestrial hypotheses.

Loeb counters, arguing that the lack of a traditional tail and observed accelerations suggest artificial propulsion.

Connection with paradox of Fermi in analysis of Loeb

The Fermi paradox questions the absence of evidence of intelligent life in a vast universe, a recurring theme in Loeb’s discussions about 3I/Atlas.

In his July 2025 paper, co-authored with Adam Hibberd and Adam Crowl, Loeb invokes the “dark forest hypothesis,” where civilizations hide to avoid cosmic predators.

This view explains interstellar silence and suggests that 3I/Atlas could be a hostile probe, with low but not zero probability.

Loeb estimates that, if technological, the object would require capabilities beyond human capabilities, such as stealth maneuvers during a solar eclipse.

The detection of X-rays in December 2025, for the first time in an interstellar, adds data on interactions with the solar wind.

Implications of UAPs and Initial Contact

Unidentified aerial phenomena, or UAPs, gain relevance in the context of Loeb, which sees parallels with 2021’s Pentágono reports of 144 unexplained incidents.

In an interview on December 8, 2025, Loeb warns that a first contact via 3I/Atlas could change humanity, whether as a scientific discovery or threat.

He proposes the “Loeb scale”, from 0 to 10, where 3I/Atlas scores 6, based on eight anomalies such as 16-hour brightness pulses.

Anomalies listed by Loeb in detail

Loeb compiled features that deviate from known comets observed between July and December 2025.

• Non-gravitational acceleration, possibly from high-speed jets.
• Front rather than rear glow, suggesting directed emission.
• Orbital alignment with low retrograde inclination, facilitating planetary access.
• High mass, inconsistent with random interstellar populations.
• Absence of initial cometary activity in spectroscopic analyses.
• Passages close to planets, with a probability of 0.005%.
• Post-perihelion multiple jets, extending against the solar wind.
• Periodic pulse of luminosity, uncommon in natural rocks.

These points, according to Loeb, justify additional studies with missions like Juno, in March 2026.

Reactions from the astronomical community

Astronomers like David Jewitt criticize Loeb’s claims as speculative, based on preliminary data.

In a post from November 8, 2025, Jason Wright, from Penn State, explains that uncertainties in fuzzy comet positions invalidate acceleration detections.

ESA and NASA prioritize observations from missions such as Juice and Psyche, which passed within 0.3 AU of the object in September and November 2025.

Future of investigations in 3I/Atlas

Missions like Europa Clipper detected the ion tail of 3I/Atlas between October 30 and November 6, 2025, measuring changes in the solar wind.

Loeb defends redirection of probes for close analysis, despite risks to primary missions.

In December 2025, the object reaches its closest point to Terra, at 1.8 AU, allowing final ground-based observations before its departure.

NASA’s SPHEREx collected data for a week, focusing on chemical composition to compare with distant star systems.