Astronomers have confirmed the discovery of comet 3I/ATLAS, officially designated C/2025 N1 (ATLAS), the third known interstellar object to pass through our solar system. Detected on July 1, 2025, by the ATLAS survey telescope in Chile, this comet is notable for its unbound, hyperbolic trajectory indicating an origin outside our solar system. Unlike previous interstellar visitors ‘Oumuamua (2017) and Borisov (2019), 3I/ATLAS exhibits a clear coma and tail typically associated with cometary activity, suggesting it is active as it approaches the Sun.
Scientists estimate the nucleus size to range from roughly 0.8 to 24 kilometers, likely on the smaller side due to surrounding dust, and the comet will reach perihelion around October 29, 2025, passing just inside the orbit of Mars. Intriguingly, research from Oxford University indicates that 3I/ATLAS may be billions of years old potentially over 7 billion making it among the oldest material ever studied, originating from the Milky Way’s thick disk of ancient stars. Its reddish hue implies it contains primordial material, serving as a time capsule for understanding planetary system formation beyond our own.
Observations from telescopes worldwide, including NASA-funded ATLAS, the Gemini North Telescope in Hawaii, and the Hubble Space Telescope, have provided detailed images revealing its compact coma and dust activity. The comet is traveling at approximately 58 km/s relative to the Sun and poses no threat to Earth. Scientists anticipate several months of observational opportunities before 3I/ATLAS resumes its journey into interstellar space, unlocking valuable insights into the galaxy’s composition and evolution.
This discovery reinforces that interstellar visitors may be more common than previously thought, with upcoming facilities like the NSF DOE Vera C. Rubin Observatory expected to find many more. 3I/ATLAS offers a unique chance to study matter formed around other stars, deepening our understanding of the cosmos.
