Discovery of Interstellar Comet 3I/ATLAS: A Glimpse into the Milky Way's Ancient Past
A remarkable animation captures the journey of comet 3I/ATLAS, a fascinating visitor from beyond our solar system. Discovered on July 1, 2025, by the NASA-funded ATLAS survey telescope in Chile, this interstellar interloper is proving to be an even more extraordinary celestial object than initially believed.
An Ancient Visitor from Distant Reaches
Comet 3I/ATLAS is significant as only the third space object observed entering our solar system from interstellar space, following in the footsteps of 1I/'Oumuamua in 2017 and 2I/Borisov in 2019. However, new research suggests that 3I/ATLAS might be significantly older than its predecessors.
University of Oxford astronomer Matthew Hopkins and his team hypothesize that 3I/ATLAS could be around 7 billion years old, potentially making it 3 billion years older than our own 4.5-billion-year-old solar system. "All non-interstellar comets, such as Halley's comet, formed at the same time as our solar system, so they are up to 4.5 billion years old," Hopkins explained. "But interstellar visitors have the potential to be far older, and of those known about so far, our statistical method suggests that 3I/ATLAS is very likely to be the oldest comet we have ever seen."
Tracing Origins to the Milky Way's Thick Disk
The key to 3I/ATLAS's advanced age lies in its origin from a different region of the Milky Way than previously observed interstellar visitors. The steep trajectory of the comet suggests it originated from the Milky Way's "thick disk" – a band composed of the galaxy's most ancient stars.
University of Oxford astrophysicist Chris Lintott commented, "This is an object from a part of the galaxy we've never seen up close before. We think there's a two-thirds chance this comet is older than the solar system, and that it's been drifting through interstellar space ever since."
Implications for Composition and Activity
If 3I/ATLAS indeed hails from the thick stellar disk, formed around an ancient star, it could have implications for its chemical composition. Scientists suggest the comet may be rich in water ice. As 3I/ATLAS approaches the sun, increased temperatures will cause its frozen ices to sublimate, turning into gas and forming the familiar cometary coma and tail.
Early observations already indicate that 3I/ATLAS is exhibiting significant cometary activity and appears to be larger than both 1I/'Oumuamua and 2I/Borisov.
Understanding Trajectories and Age
The ability of astronomers to determine the trajectory and origin of such distant objects is a testament to advancements in astronomical observation and analysis. While the concept of 'age' for celestial bodies can be complex, in the case of comets like 3I/ATLAS, when scientists refer to them as 'oldest,' they generally mean they have existed in their current form for a significantly longer period, remaining largely undisturbed.
