Recent observations from the James Webb Space Telescope indicate that the interstellar comet 3I/ATLAS may have formed approximately 10 to 12 billion years ago, potentially making it one of the oldest objects ever detected crossing the solar system.
The object known as 3I/ATLAS gained worldwide attention after being identified as an interstellar visitor traversing the solar system last year.
Initially, its passage generated speculation and debate, including online theories suggesting it might be an alien spacecraft.
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Despite these hypotheses, most astronomers have concluded that 3I/ATLAS is a comet originating from an unknown star system. Recent studies reinforce this interpretation by analyzing its composition and trajectory with greater precision.
The new analyses were preliminarily published on the Research Square preprint server and are still undergoing peer review. Even so, the data obtained offer detailed information about the comet’s possible age and origin.
Observations from the James Webb Space Telescope indicate the extreme age of 3I/ATLAS.
Scientists had already suspected that 3I/ATLAS might be extremely old due to its speed and trajectory as it traversed the solar system. These characteristics indicated that the object likely formed long before the birth of our own planetary system.
Initial estimates suggested that the comet could be between 3 billion and 11 billion years old.
However, new measurements made by the James Webb telescope have narrowed that margin and indicate an approximate age of between 10 billion and 12 billion years.
If these estimates are confirmed, 3I/ATLAS would be more than twice the age of Earth, estimated at around 4,5 billion years. Its age would also surpass that of the solar system itself, which formed approximately 4,6 billion years ago.
At the highest estimate, the comet could be close to the age of the Milky Way, calculated at around 13,6 billion years. This value also approaches the estimated age of the universe, which is around 13,8 billion years.
3I/ATLAS is only the third recorded interstellar visitor.
3I/ATLAS is only the third interstellar object identified crossing the solar system. According to observations made by the Hubble Space Telescope, the body has an estimated diameter between 440 meters and 5,6 kilometers.
The comet entered the solar system at a speed of approximately 221 kilometers per hour. After approaching the Sun, it followed a trajectory that allowed telescopes to observe its composition and behavior.
The closest point to the Sun, called perihelion, was recorded on October 29, 2025. Shortly after, on December 19, the comet made its closest approach to Earth.
At the time, 3I/ATLAS passed about 270 million kilometers from the planet. The observations made by the James Webb telescope occurred a few days later, on December 22nd.
The chemical composition of 3I/ATLAS reveals a very ancient environment of origin.
As comets approach a star, the increased temperature causes the ice on their surface to sublimate. This process transforms the ice directly into gas and releases materials that can be analyzed by scientists.
The researchers used this characteristic to study the composition of the material released by 3I/ATLAS. The analysis focused primarily on the proportion of isotopes present in the gases emitted by the comet.
The results indicated that the water present in 3I/ATLAS has higher levels of deuterium than those observed in any comet studied within the solar system. Deuterium is a heavier isotope of hydrogen.
Furthermore, the proportion of carbon isotopes found in the comet also exceeded the levels normally recorded in objects in our planetary system. This data reinforces the hypothesis that the comet formed in a different stellar environment.
According to researcher Romain Maggiolo of the Royal Belgian Institute of Space Aeronomy, the results indicate that 3I/ATLAS likely originated about 10 to 12 billion years ago in another region of the Milky Way.
Extreme formation conditions may have occurred in the early galaxy.
The data obtained by the researchers also suggest that the comet formed in an extremely cold environment. Estimates indicate temperatures around 30 Kelvin, equivalent to approximately minus 243 degrees Celsius.
This scenario suggests that 3I/ATLAS may have originated within a dense, protected protoplanetary disk. Such environments are regions where planets and other celestial bodies can begin to form.
The chemical characteristics observed in the comet also indicate the significant presence of volatile molecules. These compounds may provide clues about chemical processes that occurred in the early planetary systems of the Milky Way.
Maggiolo highlighted that these molecules may indicate that a rich prebiotic chemistry already existed in star-forming regions very early in the galaxy’s history.
The exact origin of 3I/ATLAS may never be discovered.
Even with the new measurements, scientists consider it unlikely to discover exactly in which star system 3I/ATLAS formed. The object likely traveled vast distances over billions of years through interstellar space.
Prolonged exposure to cosmic radiation may also have significantly altered its chemical composition. This process makes it even more difficult to reconstruct the exact conditions of its place of origin.
Despite these limitations, researchers emphasize that the data collected by the James Webb telescope represents an important piece in understanding this interstellar visitor. Each new measurement contributes to clarifying its history.
Comet 3I/ATLAS is already leaving the solar system.
While studies continue, 3I/ATLAS is already rapidly moving away from the solar system. The object is currently heading towards Jupiter, where it will make its closest approach to the planet on March 15.
During this passage, the comet should come within about 54 million kilometers of the gas giant. This distance is significantly less than that recorded during its closest approach to Earth.
After that, the comet will continue its journey towards the outer regions of the solar system. Projections indicate that it will cross Saturn’s orbit in July, Uranus’ orbit in April 2027, and Neptune’s orbit in March 2028.
Even as it moves away rapidly, 3I/ATLAS will continue to be monitored by astronomers. Each new observation may reveal more details about this ancient interstellar messenger that crossed our solar system.