Interstellar comet 3I/ATLAS, claimed to be an alien spacecraft, may be 7 billion years old |

When interstellar comet 3I/ATLAS was discovered by the ATLAS Survey Telescope in Chile on July 1, 2025, it quickly attracted attention for more than just being the third known object from outside the solar system. Some researchers, including Harvard astrophysicist Avi Loeb, argued that several unusual features were interesting enough to keep the possibility of artificial origins on the table, sparking widespread speculation about alien technology. Most astronomers preferred the natural explanation. Now, a new analysis by researchers at the University of Oxford suggests the body may be even more extraordinary. Their model suggests that 3I/ATLAS could be around 7 billion years old, meaning it may have formed billions of years before the Sun and could be older than our entire solar system’s 4.6 billion years old, making it likely the oldest comet ever observed.

Why do some people think that interstellar comet 3I/ATLAS could be an alien?

Shortly after the discovery of 3I/ATLAS, Harvard astrophysicist Avi Loeb and his collaborators turned it into one of the most talked-about objects in astronomy by asking whether it could be more than just a comet. In their paper, they argued that the object’s unusually high speed, steep trajectory, and other strange features are worth treating as potential signs of something very strange. The most surprising line in the paper was that 3I/ATLAS could be a “technological artifact,” and, under a “dark forest” reading of the Fermi Paradox, it might even be “hostile.”Loeb and his colleagues pointed out several details that they thought made the object unusually interesting. They said 3I/ATLAS made a surprising close pass by Venus, Mars and Jupiter, and argued that such a path could theoretically help a technological body observe planets while remaining difficult to detect from Earth. In their paper, they went further and suggested that the object’s path through the solar system, coupled with the possibility of a hidden maneuver related to the propulsion near perihelion, made it worth considering as a potential interstellar probe rather than ruling it out as a routine comet.This framing quickly captured the public’s imagination because Loeb had already become known for offering unconventional interpretations of interstellar visitors. In his later writings, he said that scientists should keep the door open to the possibility of a “Trojan horse” that might look like a rock on the outside but hide advanced technology inside, and described 3I/ATLAS as an opportunity to explore an “exciting possibility” rather than a foregone conclusion. His argument was not that the strange explanation had been proven, but that the anomalies were interesting enough to keep the idea alive.

Oxford scientists estimate that the comet may be older than the sun

The new analysis comes from Matthew Hopkins of the University of Oxford, who developed the Otutahi-Oxford model with Professor Chris Lintott and collaborators at the University of Canterbury in New Zealand. The model uses the trajectories of interstellar objects to estimate where they originated and their likely age. When Hopkins ran the newly discovered 3I/ATLAS test on the model, the results surprised even the researchers.According to the team’s findings, the probability that the comet is older than our 4.6 billion-year-old solar system is approximately two-thirds. Best statistical estimates place it at about 7 billion years old. “Our statistical method indicates that 3I/ATLAS is very likely the oldest comet we have ever seen,” Hopkins said in a statement issued by the Royal Astronomical Society.

The object probably came from the thick disk of the Milky Way

One clue to the comet’s age lies in its unusual path through the solar system.Most stars, including the Sun, belong to the thin disk of the Milky Way. Above and below it is an older cluster of stars known as the thick disk. It is believed that the age of these stars ranges between 10 to 12 billion years.Because 3I/ATLAS entered the solar system at a steep angle, the Oxford team believes it most likely originated from this ancient region of the galaxy.Professor Chris Lintott said the object “appears to come from the thick disk of the Milky Way”, giving astronomers a rare opportunity to study material that formed around stars much older than the Sun.

Why is 3I/ATLAS scientifically important?

Comets preserve ancient material from the protoplanetary disks in which they formed. If the age estimate is correct, 3I/ATLAS may contain clues about conditions that existed billions of years before our solar system formed.Preliminary observations indicate that the comet is rich in water ice and volatile compounds. Scientists hope that detailed spectroscopic studies will reveal more about the chemistry of ancient star systems and how the Milky Way Galaxy evolved over time.In this sense, 3I/ATLAS is not just another comet. It may represent one of the oldest pieces of planetary material ever observed.

The age estimate is still a possibility, not a certainty

Astronomers stress that the 7 billion year figure is not a direct measurement.No one can determine the age of a comet in the same way that geologists date rocks on Earth. Instead, the estimate comes from a statistical model based on the object’s orbit and its possible galactic origin.This means that future observations and discoveries of other interstellar objects may improve or even challenge the current estimate.However, researchers believe that 3I/ATLAS is likely to become an important benchmark for understanding objects from distant star systems.

More interstellar visitors could soon be found

Until 2017, no confirmed interstellar objects had ever been sighted. Since then, astronomers have identified “Oumuamua”, “2I/Borisov”, and now “3I/ATLAS”.The Vera C. Rubin Observatory, which has begun operations in Chile, is expected to significantly increase this number. Scientists believe that many more interstellar visitors could be discovered each year.Each new object will provide an opportunity to compare different regions of the galaxy and test the Oxford model further.As for 3I/ATLAS, it actually leaves the solar system on a one-way trip back into interstellar space. But the data collected during its brief visit may keep astronomers busy for many years to come.