Dipak Kurmi
In the vast, silent reaches of our solar system, where the Sun’s gravity reigns and celestial objects obey the familiar dance of elliptical orbits, a stranger has appeared—an ancient visitor from the deep void between stars. On July 1, 2025, astronomers using the ATLAS survey telescope in Río Hurtado, Chile, detected a new object speeding toward our solar system. Designated 3I/Atlas, this mysterious body has since gripped the imagination of scientists around the globe. More than just a scientific curiosity, it could be the oldest comet ever observed—estimated to be over seven billion years old, predating the birth of our own Solar System by nearly three billion years.
Presented to the world on July 11 at the Royal Astronomical Society’s national meeting in Durham by a team of researchers from Oxford University, 3I/Atlas marks only the third time that scientists have conclusively identified an interstellar object—a class of celestial phenomena believed to originate from beyond our Sun’s gravitational dominion. The first, 1I/ʻOumuamua, was discovered in 2017 and defied expectations with its strange, cigar-shaped geometry and tumbling motion. The second, 2I/Borisov, observed in 2019, offered a clearer view—a classic comet-like body complete with a glowing coma and icy tail. Now 3I/Atlas adds a new chapter to this emerging field, carrying with it tantalising clues about the infancy of other solar systems and the primordial matter from which they formed.
At the time of its discovery, 3I/Atlas was approximately 670 million kilometres from the Sun, just beyond the orbit of Jupiter. Since then, it has continued its course inward through the solar system, now hovering at a distance of about 917 million kilometres from Earth. Unlike asteroids or comets native to our planetary neighbourhood, whose movements are governed by elliptical orbits with both a perihelion (closest point to the Sun) and aphelion (farthest point), interstellar objects like 3I/Atlas follow a very different path—a hyperbolic trajectory. This means they pass through once, pulled slightly by the Sun’s gravity but not captured by it, and then return to the interstellar darkness from whence they came, never to return.
It is this very trajectory that first alerted astronomers to the object’s alien origin. Using sophisticated models that calculate an object’s motion through space, scientists tracked 3I/Atlas's speed and direction against the stellar background. Its velocity—an astonishing 60 kilometres per second—was far too high for an object at that distance to be gravitationally tethered to the Sun. In our solar system, the farther an object is from the Sun, the slower it tends to move. That 3I/Atlas was speeding through the outer solar system with such force suggested it had entered already in motion, likely slingshotted from a distant stellar system where a violent gravitational event—perhaps an encounter with a massive planet or binary star—ejected it into the void.
But beyond its mere trajectory and velocity, 3I/Atlas could carry within it the very chemical blueprints of another planetary system. As with 2I/Borisov, which was found to contain cyanide and carbon monoxide—key components in the formation of life—scientists now hope to analyse the chemical makeup of 3I/Atlas. If it is confirmed to be a comet, and early indications suggest that it is, its icy core may hold preserved molecules from a time and place far removed from our own. This ancient ice could offer insight into not only where the object originated, but how that system may have formed, what kind of star it orbited, and even whether prebiotic chemistry—the building blocks of life—could have been seeded similarly across the galaxy.
The notion that our solar system is not a cosmic island, but part of an interlinked web of matter exchanged across interstellar distances, is no longer science fiction. Until just a few years ago, interstellar objects were purely theoretical. Astronomers assumed they existed, based on models of planetary formation that predicted material would occasionally be flung into interstellar space. However, their detection was deemed unlikely due to the faintness, speed, and unpredictability of such objects. It was only with advancements in wide-field telescopic surveys and rapid computing techniques that the veil was lifted. The ATLAS (Asteroid Terrestrial-impact Last Alert System) project, designed originally to detect Earth-bound asteroids, has now inadvertently become a hunter of galactic wanderers.
What makes the detection of 3I/Atlas even more significant is its age. If early modelling holds true, and the object is indeed over seven billion years old, it could predate the formation of the Sun and planets. That would make 3I/Atlas not only older than Earth, but older than the very conditions that made Earth possible. This opens a window into a time when the universe was still forming its first complex molecules, when gas and dust clouds were coalescing into the earliest generations of stars and worlds. In effect, this object is a fossil of the cosmos, a relic untouched by the cosmic processes that shaped our own system.
However, challenges remain. As with ʻOumuamua, whose bizarre shape and acceleration baffled astronomers and sparked speculative theories ranging from frozen hydrogen icebergs to alien probes, interpreting data from such fast-moving objects is fraught with difficulty. Their brief appearance in the inner solar system gives scientists only a small observational window. Unlike comets that loop back around every few years or decades, interstellar objects offer a once-in-a-lifetime opportunity for close study.
The European Space Agency (ESA), in a statement about interstellar visitors, aptly remarked: "It may be thousands of years until humans visit a planet in another solar system, and interstellar comets offer the tantalising opportunity for us to touch something truly otherworldly… These wanderers offer a rare, tangible connection to the broader galaxy—to materials formed in environments entirely unlike our own."
Indeed, the implications of such discoveries are profound. With each new interstellar object, we are not only charting unknown paths across the solar system, but extending our understanding of planetary formation as a universal phenomenon. The diverse chemical and structural properties of these bodies challenge us to think beyond our local assumptions. They compel us to reimagine our place in a dynamic, interconnected galaxy where material, momentum, and perhaps even life itself may traverse unimaginable distances.
While 3I/Atlas continues its journey, soon to curve away from the Sun and vanish once more into the abyss, scientists around the world are racing to collect data—spectral signatures, light curves, and trajectory refinements—that might allow us to preserve a record of its fleeting visit. Some have even proposed future space missions to intercept interstellar objects, an idea previously considered science fiction but now inching toward feasibility with rapid developments in propulsion and autonomous tracking systems.
The detection of 3I/Atlas is a reminder that even in the cold emptiness of space, there are stories waiting to be discovered—stories written in the language of motion, light, and ice. It whispers of ancient systems, forgotten collisions, and the unseen mechanisms that bind galaxies together. As telescopes across the globe and orbit continue to track this ghostly voyager, humanity watches, humbled and curious, reaching out across the stars to understand not only where this object comes from—but perhaps, in some cosmic echo, where we do too.
(The writer can be reached at dipakkurmiglpltd@gmail.com)
