Astronomers Discover Oldest Interstellar Comet In Solar System

Astronomers have discovered a rare interstellar comet named 3I/ATLAS, which is potentially the oldest comet ever observed, estimated to be around 7 billion years old—significantly older than the 4.5-billion-year-old solar system. Detected on July 1, 2025, by the ATLAS survey telescope in Chile, this is only the third confirmed interstellar object to enter our solar system, following 1I/'Oumuamua and 2I/Borisov. Unlike typical comets formed within our solar system, 3I/ATLAS likely originated from the Milky Way's 'thick disk,' a region of ancient stars, and is notable for its steep trajectory and large size. As it approaches the Sun, its icy composition is expected to sublimate, creating a bright coma and tail visible to telescopes worldwide, including the Vera C. Rubin Observatory. This discovery opens new opportunities to study materials from distant planetary systems and suggests many more such interstellar objects may soon be detected. The comet’s unique origin and age provide valuable insights into cosmic history and the broader galaxy beyond our solar system.