Rio Hurtado, Chile (Agencies): July 3, 2025 — Astronomers have confirmed the discovery of a rare interstellar comet, officially designated 3I/ATLAS, marking only the third known object from beyond our solar system to pass through its inner regions. First detected on July 1 by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile, the comet has since sparked a global observational campaign.
Archival data from ATLAS and the Zwicky Transient Facility revealed that the object was already visible as early as June 14, approaching from the direction of the Sagittarius constellation, near the galactic center. Its hyperbolic trajectory and extraordinary speed—estimated at 68 km/s (152,000 mph)—confirm its interstellar origin.
“This thing is coming in at such an incredible speed that absolutely nothing in the Solar System could have caused this,” said Dr. Jonti Horner, astronomer at the University of Southern Queensland. Unlike typical solar system comets, which follow elliptical orbits, 3I/ATLAS is traveling on a nearly straight path, indicating it is not gravitationally bound to the Sun.
Currently located 670 million kilometers from the Sun, the comet is expected to reach perihelion on October 29, passing just inside Mars’ orbit. It will make its closest approach to Earth on December 19, at a safe distance of 270 million kilometers.
Astronomers worldwide have rushed to secure telescope time. “Almost every planetary astronomer I know immediately ran to a telescope,” said Dr. Teddy Kareta of Villanova University, who was among the first to observe the comet using the Lowell Discovery Telescope.
Signs of cometary activity—including a faint coma and short tail—were detected within 24 hours of discovery, earning the object the additional designation C/2025 N1 (ATLAS). Its estimated diameter is 12–20 kilometers, though this may change as more data is collected.
A live stream of the comet’s passage is being hosted by the Virtual Telescope Project, led by Italian astrophysicist Gianluca Masi, beginning July 3 at 6 p.m. ET.
With months of visibility ahead, astronomers hope to study the comet’s composition, behavior, and origin. As Dr. Paul Chodas of NASA’s Jet Propulsion Laboratory noted, “It must have originated from another solar system and probably has been traveling through interstellar space for millions of years”