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| Sample images showing the morphological development of 3I/ATLAS. The image dates and heliocentric distances of the comet are shown in each panel, as is a 10′′ scale bar. Sunward is West. The location of the brightest pixel is marked with a red dot, showing that the dust is extended asymmetrically towards the West in the early data, reversing to the East as the radiation pressure swept tail develops in the later data. |
On October 29, 2025, the interstellar object 3I/ATLAS reached its perihelion, its closest approach to the Sun, at precisely 7:47 AM Eastern Time. While hidden from Earth-based telescopes behind the Sun, this enigmatic visitor continues to challenge our understanding of what interstellar objects can be.
What Is 3I/ATLAS?
3I/ATLAS is the third confirmed interstellar object to enter our Solar System, following 1I/‘Oumuamua and 2I/Borisov. Unlike its predecessors, 3I/ATLAS is massive, estimated to be at least 5 kilometers in diameter and exhibits a range of anomalies that have prompted serious scientific inquiry into whether it might be of technological origin.
Could We Have Imaged It?
Yes, if Earth had been on the opposite side of its orbit. Radar systems like Goldstone’s 70-meter antenna could have captured detailed images of 3I/ATLAS had it passed within 54 million kilometers of Earth. Unfortunately, its closest approach will be 269 million kilometers on December 19, 2025, making radar detection infeasible due to the steep inverse fourth-power dependence of radio flux on distance. Put simply, 3I/ATLAS would have zipped past our most powerful detectors at a distance five times beyond their optimal range for capturing detailed imagery.
Eight Anomalies That Defy Expectations
Prof. Avi Loeb, head of the Galileo Project, has assigned 3I/ATLAS a rank of 4 on the Loeb scale (0 = definitely natural, 10 = definitely technological). Here are the eight anomalies that contribute to this ranking:
Trajectory Alignment: Its path is aligned within 5° of the ecliptic plane, a configuration with only a 0.2% likelihood.
Sunward Jet (Anti-Tail): Observed in July–August 2025, this jet defies the usual optical illusion explanation for comet tails.
Mass and Speed: It is a million times more massive than ‘Oumuamua and a thousand times more massive than Borisov, while moving faster than both, an extremely rare combination.
Fine-Tuned Arrival: Its trajectory brought it close to Mars, Venus, and Jupiter, while remaining unobservable from Earth at perihelion—a configuration with a mere 0.005% likelihood.
Nickel-Rich Plume: The gas plume contains much more nickel than iron, resembling industrial alloys, and has a nickel-to-cyanide ratio orders of magnitude higher than known comets.
Low Water Content: Only 4% water by mass, unlike typical comets.
Extreme Negative Polarization: Unprecedented among known comets, including Borisov.
Arrival Direction: Coincides within 9° of the famous “Wow! Signal” detected in 1977.
Multiplying these improbabilities yields a cumulative likelihood lower than one in ten quadrillion, suggesting that 3I/ATLAS may not be a typical comet.
What Would Confirm a Technological Origin?
Loeb suggests that if 3I/ATLAS:
Maneuvers,
Releases mini-probes,
Emits radio signals,
Displays artificial lights or excess heat,
…then we could confirm it as a technological artifact. Radio observatories are now monitoring it, and efforts are underway to release HiRISE images taken on October 2, 2025.
Why This Matters
If 3I/ATLAS turns out to be technological, it would imply capabilities far beyond our own. Starship, our largest rocket, is 100 times smaller than this object. As Loeb puts it: “Science is better than fiction, because nature might be more imaginative than the best script writers in Hollywood.”
