Interstellar Visitor
C/2025 N1 · Third Interstellar Visitor
A hyperbolic comet traveling at extraordinary speeds through space.
July 1, 2025
ATLAS Survey, Chile
Oct 29, 2025
1.357 AU from Sun
Dec 19, 2025
1.80 AU (269 million km)
Breaking news, mission updates, and fresh observations
BREAKTHROUGH
NEW
First polarimetric observations reveal -2.7% negative polarization, suggesting dust formed under conditions absent from our Solar System
Read more
mission
Interstellar comet reaches perihelion Oct 29 hidden behind the Sun. Europa Clipper and Juice prepare for unprecedented ion tail observations in November.
Read more
breakthrough
First clear water detection from an interstellar comet reveals 40 kg/s outflow from 2.9 AU—rewriting our understanding.
Read moreWhat we know about this mysterious visitor
0.32 - 5.6 km
Diameter estimated by Hubble Space Telescope. Most likely less than 1 km.
58 km/s
Hyperbolic excess velocity (v∞). Moving at 68.3 km/s at perihelion.
16.16 hours
Synodic rotation period of the nucleus.
Rich in CO₂
Contains CO₂, H₂O ice/vapor, CO, carbonyl sulfide, CN, and atomic nickel.
~700,000 km
CO₂ coma diameter. Visual coma ~26,400 × 24,700 km (twice Earth's diameter).
Reddish
B-V = 0.98±0.23. Caused by irradiated organic compounds (tholins).
3I/ATLAS likely originated from the Milky Way's thin disk or thick disk. If from the thick disk, it could be over 7 billion years old — older than our Solar System (4.6 billion years).
The comet's composition and properties suggest it formed in a distant star system and has been traveling through interstellar space for potentially billions of years.
Key events in 3I/ATLAS's journey through our Solar System
Earliest precovery detection found in archival data
ATLAS Survey at Río Hurtado, Chile discovers fast-moving object at 4.5 AU from Sun
Minor Planet Center confirms hyperbolic orbit, designated as 3I/ATLAS
Major space telescopes start detailed study of composition and structure
Detailed images reveal growing tail and coma structure
Passes within 0.0179 AU of Mars orbit
Closest approach to Sun at 1.357 AU — peak observation window
Passes Earth at safe distance of 1.80 AU (269 million km)
Exits Solar System, returning to interstellar space forever
Stunning views from world's most powerful telescopes
Scientific consensus vs. alternative hypotheses
Harvard astronomer Avi Loeb proposed that 3I/ATLAS could potentially be an artificial probe from an extraterrestrial civilization, citing:
Loeb described this as a "pedagogical exercise" to explore possibilities.
NASA, ESA, and the astronomical community confirm 3I/ATLAS is a natural comet based on:
NASA and ESA state: "3I/ATLAS displays all classical signatures of cometary activity. The overwhelming evidence points to a natural interstellar comet, not artificial technology."
The object poses no danger to Earth and will continue past our planet at a safe distance before returning to interstellar space.