Introduction: The Cosmic Visitor 3I/ATLAS
A new interstellar object was discovered by astronomers in July 2025, which is known as 3I/ATLAS (also C/2025 N1).
It's the third official interstellar visitor since 'Oumuamua and 2I/Borisov.
Its orbit is hyperbolic, which means that it is not gravitationally bound to the Sun in a traditional elliptical path.
However, over the past several months, Harvard astrophysicist Avi Loeb has proposed a hypothetical — and contentious — possibility: that 3I/ATLAS may not be just passing through but linger in our Solar System under exceptional conditions, possibly even as a technological artifact. Let's walk through his reasoning, the critiques, and what the evidence presently supports.
Avi Loeb's Hypothesis: Why It Might Stay
Loeb's argument has a few threads running through it, combining orbital mechanics, observational deviations, and theoretical likelihood. Some of these points are:
1. Alignment and Trajectory
Loeb observes that 3I/ATLAS follows an unusually aligned trajectory with respect to the ecliptic plane (the plane of the planetary orbits), suggesting that a random interstellar object would follow a much less "planet‐friendly" trajectory.
He also points to the timing of its passes by planets such as Mars, Venus, and Jupiter, claiming those alignments have very low probabilities of occurring randomly.
To his eyes, the "coincidences" may imply knowing targeting or planning — not random drift.
2. The Leading Glow and Lack of Tail
Hubble observations indicate a weak glow in front of the object (i.e. ahead of its trajectory), instead of the normal trailing tail of a comet. Loeb sees this as consistent with a "buffer zone" of particles released in front, perhaps to warn or deflect approaching debris.
At the same time, he argues that no strong gas signature (e.g. of water vapor) has been incontrovertibly detected in some datasets, which weakens the case for a “normal” comet outgassing mechanism.
He suggests that if the object were technological, its design might suppress typical cometary signatures (for example, by emitting only large dust particles or using unconventional mechanisms).
3. The “Loeb Scale” and Future Movement
Loeb has proposed a speculative "Loeb scale" (0 = certainly natural; 10 = certainly artificial) and currently assigns 3I/ATLAS a rating of 4 — i.e., a possible, though tentative, non‐natural origin.
He is willing to admit that with more data the rating could fall towards 0 (纯 comet) or climb towards 10 (certain technology).
Regarding staying in the Solar System: though 3I/ATLAS’s path is hyperbolic (which normally means an “escape” trajectory), Loeb’s scenario leaves open that some interactions — or engineered maneuvers — might slow or alter its escape, allowing it to linger or even be captured in a weak bound orbit under special circumstances.
Criticisms & Counterarguments: Why Most Scientists Remain Skeptical
Loeb's hypothesis has drawn both interest and criticism. Here are the primary counterarguments from the scientific community and accessible observations:
1. Hyperbolic Orbit Suggests No Capture in the Long Term
A fundamental physical reality: 3I/ATLAS is right now on a hyperbolic orbit, which means its trajectory is not gravitationally bound to the Sun without external forces.
To transition a hyperbolic orbit into a bound or lingering path would necessitate nontrivial energy modifications — i.e., through substantial gravitational encounters or propulsive actions. Such modifications are hypothetical and at present are not data-supported.
2. Detection of Gas and Coma Behavior
Recent discoveries, such as the James Webb Space Telescope (JWST) observations, have seen a CO₂-rich coma around 3I/ATLAS, as well as weak signals of water (H₂O), CO, OCS, and dust.
That conclusion violates the "no gas" hypothesis and is consistent with typical cometary behavior, but with abnormally high proportions (CO₂/H₂O ratio).
Opponents claim that brightness profiles and spectral properties cited by Loeb can be explained by dust emission, large grains, or other intrinsic processes.
3. Statistical and Interpretative Issues
Some astronomers have criticized Loeb's probabilistic reasoning, arguing that his estimates of "low probability" occurrences are susceptible to selection effects (i.e. we observe the interesting ones) and hindsight bias.
Others assert that appealing to an artificial origin diverts attention from the more substantive scientific challenge: grasping interstellar comet diversity.
4. NASA & Broader Scientific Position
NASA and most planetary scientists still view 3I/ATLAS as a natural interstellar comet, rather than an extraterrestrial spacecraft.
Critics note that, to date, none of Loeb's postulated "technological signatures" have been established in any manner that definitively eliminates natural causes.
In fact, even Loeb himself has termed his suggestions as a "pedagogical exercise" — a thought experiment — and not an absolute conclusion.
Then — Will 3I/ATLAS Remain Within Our Solar System?
Based on evidence and arguments:
The default prediction, following orbital mechanics, is that 3I/ATLAS will eventually depart from our Solar System on a hyperbolic escape trajectory.
Loeb's scenario is not standard — it is speculative, dependent on numerous unproven or doubtful steps (e.g. artificial thrust, course maneuvers, concealed design).
Current observations (particularly the JWST detection of CO₂ and water) are more consistent with the idea that 3I/ATLAS is acting as a strange but normal interstellar comet.
Therefore, although it's not inconceivable (in theoretical speculation) that a future interaction or adjustment might slow or change its exit, there is no convincing evidence at present that it will stay.
Short version: Loeb's assertion is intriguing and
provocative — a "what if" that challenges assumptions — but it exists
on the outskirts until more robust, clear evidence surfaces.
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