Interstellar comet 3I/Atlas may be the oldest object observed in our solar system

A new study published in Nature suggests that the interstellar comet 3I/Atlas, which streaked past the Sun in 2025, could be up to three times older than the Solar System itself, making it potentially the oldest object ever observed within our planetary neighborhood.

Discovery and Unprecedented Brightness of 3I/Atlas

The comet is only the third known interstellar visitor after 1I/’Oumuamua (2017) and 2I/Borisov (2019). Spotted in July 2025, its exceptional brightness allowed astronomers to gather isotopic data that were impossible for the earlier objects. Early online speculation, including a claim by a Harvard researcher that the object could be an alien spacecraft, was dismissed by NASA and SETI.

Isotopic Measurements Reveal a 12‑Billion‑Year Age

Observations with the James Webb Space Telescope and the ALMA observatory measured a deuterium abundance ten times higher than that of typical Solar‑System comets. The isotopic signature points to formation in an extremely cold environment of about -243°C (-405.4°F), and the authors estimate an age of up to 12 billion years, compared with the Solar System’s age of 4.5 billion years. Lead author Martin Cordiner of NASA’s Goddard Space Flight Center described the object as “maybe the oldest object to have been observed in our solar system”.

Implications for Galactic Chemistry and Early Cosmic Epochs

The comet’s lack of chemical enrichment suggests it formed close to newborn stars, possibly during the “cosmic noon” era roughly 10 billion years ago when star formation peaked in the Milky Way. Its trajectory, untethered to any star, implies billions of years spent on “vast unimaginable trajectories” around the galaxy, offering a rare glimpse into the material that seeded early planetary systems.

Future Prospects for Interstellar Object Research

With the upcoming Vera C. Rubin Observatory in Chile, astronomers expect to detect many more interstellar interlopers, turning this single discovery into the opening act of a new field. As Peter Veres of the International Astronomical Union notes, the comet is now exiting the Solar System and will not return, making timely follow‑up observations critical.