Preface: Avi Loeb speculates that 3I/ATLAS has a diameter of at least 5 kilometers and a mass of over 33 billion tons, although his models suggest the nucleus could be as large as 15 kilometers in diameter. He bases these estimates on the object’s lack of a non-gravitational acceleration, which indicates it’s a massive object, and on data from the Hubble Space Telescope.
On October 19, 2025, Avi Loeb is likely commenting on the near-perihelion approach of the interstellar object 3I/ATLAS and the recent analysis of its properties, particularly focusing on anomalies like its unusual chemical composition and trajectory that he argues suggest a potential artificial origin.
Background: According to NASA’s announcement, we have to say goodbye to this comet! However, Professor Loeb has also uncovered many unsolved mysteries. Because 3I/ATLAS is so far away from Earth, even the Hubble Space Telescope can only see a bright spot. Current parameters are derived from predictions and analysis of the solar spectrum. This is based on some unknowns (see below). Perhaps we can add our own imaginations as a record. Given the current timeline, we may only see this comet once in our lifetime!
a. The spectral analysis of the interstellar object 3I/ATLAS has shown the presence of atomic nickel vapor and cyanide gas in its tail, with preliminary findings also indicating an unusual abundance of nickel without iron. The high nickel-to-iron ratio is considered anomalous compared to naturally occurring comets and has led to speculation about the object’s origins.
Ref: Nickel is essential in space and nuclear power due to its high-temperature resistance, corrosion resistance, and mechanical strength. In space, nickel alloys are used in rocket engines, fuel tanks, and batteries, while in nuclear power, they are used for structural components, fuel rod cladding, and steam generators.
b. Comet 3I/ATLAS exhibits an unusual “anti-tail” that points toward the Sun.
c. While Loeb has theorized that 3I/ATLAS could be an alien probe, his team’s observations of the comet and its environment so far have not revealed any such fragment. Current images show faint features that are likely noise or other unrelated objects, and the team is continuing to monitor the object for any signs of disintegration.
Professor Loeb’s recent research on 3I/ATLAS: Please see the link for details –