The recently identified interstellar object 3I/ATLAS is generating significant excitement among astronomers. This cosmic traveler, which marks only the third confirmed interstellar object to enter our solar system, was first detected on July 1, 2025, by the remote Deep Random Survey telescope located in Chile, part of the ATLAS (Asteroid Terrestrial-impact Last Alert System) initiative.
Officially designated as C/2025 N1 (ATLAS), this rare find has captured the attention of researchers due to its unique characteristics. Initially referred to by the temporary name A11pl3Z, 3I/ATLAS was swiftly recognized for its unusual trajectory. Subsequent observations confirmed that the object is not bound by the sun’s gravity, establishing it as an interstellar entity—joining the ranks of 1I/’Oumuamua in 2017 and 2I/Borisov in 2019.
“If confirmed, it will be the third known interstellar object from outside our solar system that we have discovered, providing more evidence that such interstellar wanderers are relatively common in our galaxy,” said Mark Norris, a Senior Lecturer in Astronomy at the University of Central Lancashire, in comments to Space.com.
What sets 3I/ATLAS apart is its status as the largest and brightest interstellar object observed to date, potentially offering insights into the formation of distant star systems.
The object’s hyperbolic orbit is the key indicator of its interstellar origin. Its trajectory includes an eccentricity of 6.2, indicating it is on a path that will not return to the sun and originates from interstellar space. For comparison, 1I/’Oumuamua had an eccentricity of about 1.2, while 2I/Borisov exhibited an eccentricity of 3.6. “Some long-period comets could have a brush with Jupiter that modifies its orbit to 1.05, i.e., hyperbolic on the way out, but just barely,” Olivier Hainaut, an astronomer at the European Southern Observatory, explained further.
In terms of size, 3I/ATLAS significantly surpasses its predecessors, measuring approximately 15 kilometers (9 miles) in diameter, though estimates may vary. In contrast, 1I/’Oumuamua was around 100 meters, and 2I/Borisov was less than 1 kilometer in diameter.
3I/ATLAS is classified as a comet due to the emergence of a comet-like coma and tail post-discovery. This led to its additional designation as C/2025 N1 (ATLAS).
In terms of safety, 3I/ATLAS currently lies within Jupiter’s orbit, about 323 million miles (520 million kilometers) from Earth, and will approach to roughly 167 million miles (270 million km) on December 19. At no point will it pose a threat, getting no closer than 18 million miles (30 million km) to Mars on October 2.
Visibility of 3I/ATLAS is restricted to those with specialized equipment; it resides in the constellation Sagittarius and is currently about 2.5 million times fainter than the North Star, requiring significant telescope capabilities for observation. However, as the object gets nearer, it is expected to brighten and become more accessible to amateur astronomers.
Professional observatories, particularly those in the Southern Hemisphere, are anticipated to capture extensive images of 3I/ATLAS. The ongoing assessments of the object are crucial, as much of the current knowledge is grounded in preliminary observations. Hainaut emphasized the urgency: “We are scrambling to get the big guys on it as soon as possible.”
The significance of 3I/ATLAS is tied to its sheer size, offering an unprecedented opportunity to study the chemical signatures from outside our solar system, which could illuminate planetary system formation and hint at the possibility of life elsewhere. “They undoubtedly carry chemical signatures from outside the solar system, so gaining observations tells us a lot about the possibility of material traveling between planetary systems,” Barstow explained.
Though the prospect of sending a spacecraft to intercept 3I/ATLAS appears unlikely due to its high speed, advancements in space missions, like the European Space Agency’s Comet Interceptor project set for launch in 2029, may pave the way for future exploration of such interstellar visitors.
The increasing identification of interstellar objects like 3I/ATLAS is partly due to advancements in telescope technology. The new Vera C. Rubin Observatory, for example, could unveil more interstellar wanderers over its operational lifespan. Recent estimates suggest that up to seven interstellar objects could pass within an Earth-sun distance annually, with many having gone undetected until now. “It will be a dramatic improvement,” Hainaut predicted. “Get ready for 4I, 5I … 42I!”
While 3I/ATLAS stands out as the most prominent interstellar visitor to date, it is likely not the last to be discovered.
