Summary
University of Oxford researchers Matthew Hopkins (PhD) and co-author Chris Lintott used the Ōtautahi-Oxford Model — a statistical framework for inferring interstellar object origins from orbital trajectories — to conclude that 3i-atlas has approximately a two-thirds probability of being older than the Solar System, with a best estimate of ~7 billion years. The key diagnostic is 3I/ATLAS’s steep approach angle, which traces back to the Milky Way’s galactic thick disk — an older stellar population orbiting on inclined paths, typically 10–12 billion years old. Unlike 1i-oumuamua and 2I/Borisov (both thin-disk, solar-age or younger), 3I/ATLAS is the first confirmed interstellar object sampled from thick-disk material. Its water-ice-rich chemistry and enhanced volatiles are consistent with formation around an older, lower-metallicity star. The Vera C. Rubin Observatory, now beginning operations, is expected to detect multiple interstellar objects per year. Note on age discrepancy: A JWST isotopic study (src-3i-atlas-jwst-isotopic-age-2026-06) published the same week gives an estimate of up to ~12 billion years; the two approaches (orbital trajectory vs. isotopic abundance) are methodologically distinct and the discrepancy is unresolved.
Key Claims
- Ōtautahi-Oxford Model gives 3I/ATLAS a ~two-thirds probability of being older than the Solar System; best statistical estimate ~7 billion years.
- Steep approach angle traces to the galactic thick disk, not the thin disk where the Sun and prior interstellar visitors originated.
- 3I/ATLAS is the first confirmed interstellar object with trajectory traced to the galactic thick disk — the oldest stellar population dense enough to plausibly source observable interstellar comets.
- Water-ice-rich composition with enhanced volatiles consistent with formation around an older, lower-metallicity star.
- Comets are “frozen samples” of protoplanetary disc chemistry; 3I/ATLAS preserves galactic chemistry from ~7 billion years ago.
- Hopkins defended his PhD one week before 3I/ATLAS discovery; developed the model with Lintott and University of Canterbury colleagues.
- Vera C. Rubin Observatory expected to detect several interstellar objects per year, enabling ongoing testing of the model.
Notable Quotes
“3I/ATLAS has approximately a two-thirds probability of being older than the solar system, with a statistical best estimate of approximately 7 billion years.” — Royal Astronomical Society (summarizing Hopkins-Lintott analysis)