The third interstellar visitor is far larger and faster than its predecessors

Space · Published 23 October 2026 Swipe more like this →

In short: After 'Oumuamua and Borisov, a new cosmic traveler has arrived. 3I/ATLAS is not just another visitor; its extreme trajectory and massive scale suggest that the wanderers passing through our solar system might be more common—and much more significant—than we once thought.

First detected on July 1, 2025, by the ATLAS survey telescope in Chile, 3I/ATLAS (also designated C/2025 N1) is the third known object to enter our solar system from interstellar space. Unlike the first two visitors, 1I/'Oumuamua and 2I/Borisov, this object follows a highly hyperbolic path with an eccentricity of 6.2. In orbital mechanics, any eccentricity above 1 indicates a path that is not gravitationally bound to the Sun, meaning the object will eventually exit our celestial neighborhood. This high eccentricity significantly outpaces the 1.2 eccentricity of 'Oumuamua and the 3.6 of Borisov.

The physical scale of 3I/ATLAS is equally striking. While 'Oumuamua was roughly 100 meters across and Borisov was less than 1 kilometer, 3I/ATLAS is much larger. While measurements are still being refined, some estimates suggest a diameter as large as 15 kilometers (9 miles), and potentially up to 20 kilometers (12 miles). Conversely, other observations, including data from the Hubble Space Telescope, suggest the nucleus could be as small as 440 meters (1,444 feet) across, with an upper limit of about 5.6 kilometers (3.5 miles).

As the comet passed near the Sun around October 30, 2025, at a distance of 1.4 au, it remained a primary target for NASA's fleet of spacecraft. Observations from the Perseverance rover and Mars orbiters captured images of the object from unprecedented proximity. Though the comet's path brought it within 1.8 astronomical units of Earth, it posed no threat to our planet. Astronomers continue to study the teardrop-shaped dust cocoon revealed by Hubble to unlock secrets about the formation of distant star systems.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• A cosmic traveler from another star system has just passed by
• A second interstellar visitor is approaching our solar system
• A cosmic traveler from another star system has just passed by
• A cosmic interloper is rewriting our map of the galaxy
• A celestial outsider from another star system just visited our neighborhood
• Beyond the Habitable Zone: JWST Unveils Worlds of Sand and Methane
• From stellar flares to the birth of the universe
• NASA's upcoming Roman Space Telescope promises a sweeping, high-resolution view of our vast universe.
• From rogue wanderers to engineered worlds: the diversity of solar systems
• The violent origins and complex construction of our solar system
• The celestial anomalies that challenge our understanding of physics
• Earth may have been seeding Venus with life for billions of years

More in Astronomy · More in Space · Latest · A–Z · All topics