Astronomers Identify Third Interstellar Visitor to Our Solar System

For only the third time in history, astronomers have detected an interstellar object racing through our Solar System. The recently identified space rock, named 3I/ATLAS (where I stands for interstellar) or C/2025 N1, could measure up to 20 kilometers in diameter.

Previously, we were only aware of two other interstellar objects that visited our Solar System — Oumuamua and comet 2I/Borisov. The nature of Oumuamua remains a topic of debate, while the second was a comet from another solar system. Now we have a third interstellar visitor on our hands. The trajectory of this object suggests that it did not originate from our system.

The International Astronomical Union’s Minor Planet Center officially added this object to its list of confirmed near-Earth objects on July 1, 2025. It is also listed on the NASA/JPL website under «Confirmed Earth-approaching objects» with the identifier A11pl3Z. Despite being classified as a near-Earth object, there are no concerns about it colliding with Earth or even coming particularly close.

It is likely either a comet or an asteroid, with current data leaning towards it being a comet.

Astrafoxen, a senior astrophysics student from California, shared an image of A11pl3Z obtained during the Deep Random Survey in Chile. Additionally, Sam Dean, a prolific amateur astronomer, discovered earlier images of the object from ATLAS data collected between June 25 and June 29. This information helps clarify the object’s trajectory, reinforcing the notion that it is almost certainly interstellar.

This faint cosmic rock currently has a magnitude of 18.8. Our new guest will reach its closest point to the Sun (about 2 astronomical units) in October. When it hits perihelion—the point nearest to the Sun—it will travel at approximately 68 kilometers per second relative to the Sun.

Marshall Uebanks, a physicist and radio astronomer with VLBI who co-founded Space Initiatives, noted in the Minor Planet mailing list that the object will approach Mars at around 0.4 astronomical units, making it barely detectable to the Mars Reconnaissance Orbiter. According to Uebanks, with current orbital data, this object originates from the thin galactic disk. «Take note that in April of next year (2026), its speed relative to Earth will reach about 90 kilometers per second. This is expected to set a record,» he added.