NASA and the European Space Agency have confirmed that a body discovered on 1 July by the Asteroid Terrestrial-impact Last Alert System telescope in Chile is an interstellar comet. Now officially catalogued by the Minor Planet Center as 3I/ATLAS, the visitor is only the third object ever observed entering the solar system from another star system, following ʻOumuamua in 2017 and comet 2I/Borisov in 2019. 3I/ATLAS is racing through space at roughly 60–66 kilometres per second and is currently about 4.5 astronomical units—or 420 million miles—from the Sun. Calculations show it will swing inside Mars’ orbit on 30 October, passing the Sun at about 1.4 AU before heading back into interstellar space. The comet will remain at least 1.6 AU, or 150 million miles, from Earth, so scientists say it poses no threat. Early observations suggest a nucleus 10–30 kilometres across cloaked in a faint coma, with spectroscopy pointing to abundant water ice and complex organic compounds. Dynamical modelling by astronomers at the University of Oxford indicates the object’s trajectory and velocity are consistent with an origin in the Milky Way’s thick disk, implying it could be more than 7 billion years old—potentially the oldest comet ever examined. Researchers worldwide are marshalling ground- and space-based telescopes to track 3I/ATLAS before it is lost in solar glare in September and again after it re-emerges in December. The rare find underscores expectations that next year’s start-up of the Vera C. Rubin Observatory could sharply increase the rate at which interstellar wanderers are detected.