Speed, Mass, and an Unstable Composition
Where Borisov behaved like a textbook comet—a ball of frozen gases and dust shedding material predictably as it neared the Sun—3I/ATLAS is rewriting the rulebook.
Astrophysicists estimate that 3I/ATLAS is at least four times larger in diameter and significantly denser. Its acceleration curve doesn’t match solar radiation pressure alone, hinting that its structure could contain metallic or composite materials that behave differently under heat and gravity.
In layman’s terms, Borisov sublimated like a snowball near a fire. 3I/ATLAS is acting more like a molten meteorite that refuses to melt, maintaining shape and speed through regions where Borisov began to fragment.
Different Origins, Different Stories
Harvard astrophysicists Amir Siraj and Avi Loeb predicted in a 2021 Monthly Notices of the Royal Astronomical Society study that our solar system should host countless interstellar visitors originating from vastly different star-forming regions. Borisov’s chemical signature pointed to a system rich in carbon monoxide and other volatile ices—evidence of birth in a cold, outer planetary disk.
3I/ATLAS, by contrast, exhibits light-spectrum anomalies suggesting a hotter, inner-disk origin, possibly from a planetary system that experienced a violent ejection event.
If verified, that would make it the first interstellar object known to carry material forged under high-temperature stellar conditions, giving researchers an unprecedented sample of exoplanetary crust.
