What is 3I/Atlas and why is it in the spotlight?
Interstellar object 3I/Atlas is attracting intense interest because it is the first known object to travel through our solar system from outside the Sun’s gravity well. It was first observed on July 1 by Chile’s ATLAS Survey Telescope, and subsequent views from the James Webb Space Telescope, the Hubble Space Telescope, and the Very Large Telescope have added to the curiosity. The big questions revolve around what 3I/Atlas actually is — a comet, an asteroid, or something more mysterious — and what its journey through our neighborhood might reveal about the rest of the galaxy.
Where did 3I/Atlas come from?
Scientists have not reached a consensus on its origin. Some data hint that it may be coming from the center of the Milky Way, while other analyses suggest it could have been pulled from the thick disk or the thin disk of our galaxy. What is clear is that 3I/Atlas is on a hyperbolic path that will take it through the inner solar system and then eject it back into interstellar space, never to return.
How old could 3I/Atlas be?
Early estimates place 3I/Atlas as one of the oldest objects observed by humans, with some scientists proposing a possible age range of roughly 7.6 to 14 billion years — older than the Sun’s 4.6-billion-year history. If confirmed, this would make the object a remarkable relic from the early universe, providing a rare glimpse into materials and processes from before the solar system formed.
How big is 3I/Atlas, and how heavy might it be?
Size is the subject of vigorous debate. Traditional interpretations from some observers suggest a modest size on the order of a kilometer in diameter. However, proponents of larger-scale interpretations, including Avi Loeb, point to analyses of Hubble and Webb data that indicate a much larger body — potentially tens of kilometers across. A related line of inquiry from researchers like Loeb, Cloete, and Veres argues that the mass must exceed about 33 billion tons and that the solid-density nucleus could have a diameter larger than 5 kilometers. In short, the exact dimensions remain unsettled and a matter of ongoing study.
What is its trajectory and timing?
3I/Atlas is currently approaching the inner solar system and is projected to pass by the planets and the Sun before moving away again. The most anticipated moment for Earth observers is its closest approach, estimated to be around 1.8 astronomical units (about 273 million kilometers) in December 2025. After its closest pass, it will continue outward, eventually leaving the solar system on a one-way journey.
What have the major telescopes revealed?
Observations from ground-based facilities and space telescopes have provided critical data on its trajectory, brightness, and composition. The ATLAS survey’s initial detection sparked rapid follow-up with the James Webb Space Telescope, the Hubble Space Telescope, and the Very Large Telescope. Each instrument has helped to constrain its velocity, trajectory, and some physical properties, though definitive conclusions about composition and origin remain elusive.
Does 3I/Atlas pose a threat to Earth?
Current projections anticipate that 3I/Atlas will pass at a safe distance, with no imminent risk to Earth. Its path is hyperbolic, meaning it will not become bound to the Sun. Nonetheless, the object provides a unique opportunity to study material from another star system and informs our understanding of how such interstellar visitors travel through galactic space.
What comes next for observers and researchers?
Researchers will continue to comb through four months of observational data and plan additional measurements as 3I/Atlas recedes. An important goal is to refine estimates of its size, mass, and composition, as well as to compare observations from different observatories. By December 2025, we should have a clearer sense of its trajectory and lingering physical characteristics, while the broader question of its origin may still invite debate.
Bottom line
3I/Atlas has opened a window into interstellar space with its unusual journey through the solar system. While many questions remain—especially regarding its exact size and origin—the object already challenges our assumptions about how common such visitors might be and what they can teach us about the rest of the galaxy.
