Astronomers have discovered an ancient, ice-rich interstellar object called 3I/ATLAS , which could transform our understanding of how comets form and evolve. Detected by the University of Oxford’s research team, this mysterious object is believed to have originated far beyond our solar system, possibly more than seven billion years ago. Its immense age suggests it predates the Sun and planets, making it potentially the oldest comet ever observed. Unlike typical comets formed within our solar system, 3I/ATLAS appears to originate from the Milky Way’s thick disk, a region rich in ancient stars. Scientists say its composition and trajectory could provide vital clues about the early galaxy and the interstellar processes that shaped the formation of stars and planetary systems.
3I/ATLAS: A rare visitor from beyond our solar system identified
The discovery of 3I/ATLAS marks only the third time astronomers have identified an object entering our solar system from interstellar space. Unlike previous visitors 1I/ʻOumuamua (2017) and 2I/Borisov (2019), this comet is thought to have originated from a completely different region of the Milky Way Galaxy.
According to Dr Matthew Hopkins, an astronomer at the University of Oxford, the object’s orbit indicates it came from the galaxy’s thick disk, a vast area populated by ancient stars. This region lies above and below the thin, flat plane where the Sun and most stars reside. Hopkins presented the findings at the Royal Astronomical Society’s National Astronomy Meeting 2025 in Durham.
“All comets within our solar system, such as Halley’s, formed about 4.5 billion years ago,” said Hopkins. “But interstellar comets like 3I/ATLAS may have formed long before that, potentially making this the oldest comet ever observed.”
Discovery of 3I/ATLAS
The object was first detected on 1 July 2025 by the ATLAS survey telescope in Chile. At the time, it was about 670 million kilometres from the Sun, travelling on a steep and unusual orbit that immediately caught astronomers’ attention.
Hopkins and his team applied a statistical model originally developed during his doctoral research, which predicts the age and composition of interstellar comets based on their orbits and likely stellar origins. Their analysis indicated that 3I/ATLAS likely formed around an ancient, thick-disk star, suggesting it contains a high concentration of water ice.
“This is an object from a part of the galaxy we’ve never seen up close before,” said Professor Chris Lintott, co-author of the study and presenter of BBC’s The Sky at Night. “There’s a two-thirds chance this comet is older than the solar system itself, a true relic from our galaxy’s distant past.”
3I/ATLAS shows early signs of activity as it nears the sun
As 3I/ATLAS moves closer to the Sun, scientists expect it to become more active. The increasing heat will cause sublimation, the release of gas and dust from its icy surface, producing a bright coma and tail, the hallmarks of a comet.
Initial observations already show signs of such activity, hinting that 3I/ATLAS could be larger and more dynamic than its predecessors ʻOumuamua and Borisov. This makes it a valuable target for upcoming astronomical missions.
According to Dr Michele Bannister from the University of Canterbury in New Zealand, “We’re entering an exciting phase. As 3I warms up under the Sun’s light, we’ll be able to study the gases it releases, providing a rare glimpse into material formed in another part of the Milky Way.”
What makes 3I/ATLAS comet more significant
The potential age of 3I/ATLAS sets it apart. Formed around ancient stars, it may carry chemical signatures from the early Milky Way, preserving information about the conditions that existed long before the Sun was born. Studying its composition could offer insights into how interstellar comets contribute to star and planet formation throughout the galaxy.
Moreover, its trajectory shows that it travels deep into the outer thick disk, a region rarely sampled by astronomical observations. The Sun, by contrast, orbits closer to the galactic plane, highlighting how extraordinary it is for material from such a remote area to reach our neighbourhood.
3I/ATLAS discovery sparks hope for more interstellar finds
The timing of 3I/ATLAS’s discovery is particularly striking. Hopkins and his colleagues were preparing for survey operations with the Vera C. Rubin Observatory, expected to transform our understanding of transient cosmic objects.
“The Rubin Observatory is projected to detect between five and fifty interstellar objects in the coming years,” explained Dr Rosemary Dorsey from the University of Helsinki. “But the discovery of 3I suggests we may find even more, perhaps dozens of these ancient wanderers.”
The Rubin telescope, with its wide-field imaging capability, will allow astronomers to track interstellar objects in greater detail than ever before. Such discoveries could redefine how we think about the origins of comets and their role in spreading organic materials across galaxies.
3I/ATLAS discovery turns Hopkins’ research into reality
Ironically, the discovery came just a week after Hopkins defended his doctoral thesis, which focused on modelling interstellar comet populations. He had planned a quiet holiday but was instead met with a flurry of messages after 3I/ATLAS was confirmed.
“Rather than a calm Wednesday, I woke up to messages saying ‘3I!!!!!!!!!!’,” he recalled. “It’s thrilling to test our theoretical model on a brand-new, possibly ancient object in real time.”
The team has since published its analysis as a preprint on arXiv, introducing the Ōtautahi–Oxford Model, the first predictive framework successfully applied to a newly discovered interstellar comet.
How and when to see 3I/ATLAS
For astronomy enthusiasts eager to witness history, 3I/ATLAS should become visible through medium-sized amateur telescopes by late 2025 and early 2026, depending on its brightness and activity.
As it continues its journey through our solar system, scientists hope it will reveal more about the ancient origins of comets, the evolution of galaxies, and the interstellar chemistry that may one day explain how life began in the universe.
Also Read | 3I/ATLAS sending mysterious Fibonacci-pattern pulse signal 8 • 13 • 8 • 5 • 13 • 8 at 1420 MHz; could it be a message from deep space
3I/ATLAS: A rare visitor from beyond our solar system identified
The discovery of 3I/ATLAS marks only the third time astronomers have identified an object entering our solar system from interstellar space. Unlike previous visitors 1I/ʻOumuamua (2017) and 2I/Borisov (2019), this comet is thought to have originated from a completely different region of the Milky Way Galaxy.
According to Dr Matthew Hopkins, an astronomer at the University of Oxford, the object’s orbit indicates it came from the galaxy’s thick disk, a vast area populated by ancient stars. This region lies above and below the thin, flat plane where the Sun and most stars reside. Hopkins presented the findings at the Royal Astronomical Society’s National Astronomy Meeting 2025 in Durham.
“All comets within our solar system, such as Halley’s, formed about 4.5 billion years ago,” said Hopkins. “But interstellar comets like 3I/ATLAS may have formed long before that, potentially making this the oldest comet ever observed.”
Discovery of 3I/ATLAS
The object was first detected on 1 July 2025 by the ATLAS survey telescope in Chile. At the time, it was about 670 million kilometres from the Sun, travelling on a steep and unusual orbit that immediately caught astronomers’ attention.
Hopkins and his team applied a statistical model originally developed during his doctoral research, which predicts the age and composition of interstellar comets based on their orbits and likely stellar origins. Their analysis indicated that 3I/ATLAS likely formed around an ancient, thick-disk star, suggesting it contains a high concentration of water ice.
“This is an object from a part of the galaxy we’ve never seen up close before,” said Professor Chris Lintott, co-author of the study and presenter of BBC’s The Sky at Night. “There’s a two-thirds chance this comet is older than the solar system itself, a true relic from our galaxy’s distant past.”
3I/ATLAS shows early signs of activity as it nears the sun
As 3I/ATLAS moves closer to the Sun, scientists expect it to become more active. The increasing heat will cause sublimation, the release of gas and dust from its icy surface, producing a bright coma and tail, the hallmarks of a comet.
Initial observations already show signs of such activity, hinting that 3I/ATLAS could be larger and more dynamic than its predecessors ʻOumuamua and Borisov. This makes it a valuable target for upcoming astronomical missions.
According to Dr Michele Bannister from the University of Canterbury in New Zealand, “We’re entering an exciting phase. As 3I warms up under the Sun’s light, we’ll be able to study the gases it releases, providing a rare glimpse into material formed in another part of the Milky Way.”
What makes 3I/ATLAS comet more significant
The potential age of 3I/ATLAS sets it apart. Formed around ancient stars, it may carry chemical signatures from the early Milky Way, preserving information about the conditions that existed long before the Sun was born. Studying its composition could offer insights into how interstellar comets contribute to star and planet formation throughout the galaxy.
Moreover, its trajectory shows that it travels deep into the outer thick disk, a region rarely sampled by astronomical observations. The Sun, by contrast, orbits closer to the galactic plane, highlighting how extraordinary it is for material from such a remote area to reach our neighbourhood.
3I/ATLAS discovery sparks hope for more interstellar finds
The timing of 3I/ATLAS’s discovery is particularly striking. Hopkins and his colleagues were preparing for survey operations with the Vera C. Rubin Observatory, expected to transform our understanding of transient cosmic objects.
“The Rubin Observatory is projected to detect between five and fifty interstellar objects in the coming years,” explained Dr Rosemary Dorsey from the University of Helsinki. “But the discovery of 3I suggests we may find even more, perhaps dozens of these ancient wanderers.”
The Rubin telescope, with its wide-field imaging capability, will allow astronomers to track interstellar objects in greater detail than ever before. Such discoveries could redefine how we think about the origins of comets and their role in spreading organic materials across galaxies.
3I/ATLAS discovery turns Hopkins’ research into reality
Ironically, the discovery came just a week after Hopkins defended his doctoral thesis, which focused on modelling interstellar comet populations. He had planned a quiet holiday but was instead met with a flurry of messages after 3I/ATLAS was confirmed.
“Rather than a calm Wednesday, I woke up to messages saying ‘3I!!!!!!!!!!’,” he recalled. “It’s thrilling to test our theoretical model on a brand-new, possibly ancient object in real time.”
The team has since published its analysis as a preprint on arXiv, introducing the Ōtautahi–Oxford Model, the first predictive framework successfully applied to a newly discovered interstellar comet.
How and when to see 3I/ATLAS
For astronomy enthusiasts eager to witness history, 3I/ATLAS should become visible through medium-sized amateur telescopes by late 2025 and early 2026, depending on its brightness and activity.
As it continues its journey through our solar system, scientists hope it will reveal more about the ancient origins of comets, the evolution of galaxies, and the interstellar chemistry that may one day explain how life began in the universe.
Also Read | 3I/ATLAS sending mysterious Fibonacci-pattern pulse signal 8 • 13 • 8 • 5 • 13 • 8 at 1420 MHz; could it be a message from deep space
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