Astronomers have identified an object originally catalogued as A11pl3Z and now formally designated 3I/ATLAS, confirming it as only the third interstellar body ever observed transiting the solar system. The comet was first detected on 1 July by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Río Hurtado, Chile; its interstellar nature was ratified this week by the International Astronomical Union’s Minor Planet Center and announced by both the European Space Agency and NASA. Current measurements indicate the icy nucleus spans roughly 10 to 20 kilometres and is racing through space at about 60 kilometres per second—far too fast to be captured by the Sun’s gravity. Now roughly 420 million miles from Earth near Jupiter’s orbit, 3I/ATLAS will swing inside Mars’ orbit on 30 October, reaching perihelion at 1.4 astronomical units and coming no nearer than 1.6 AU (around 150 million miles) to our planet. Researchers say the trajectory poses no danger to Earth. Dynamical modelling suggests the comet originated in the Milky Way’s thick disk and may be more than seven billion years old, potentially making it the oldest comet yet recorded. Preliminary spectroscopy points to a water-ice-rich composition laced with organic dust, offering scientists an unprecedented look at primordial material from another star system. Observatories worldwide—including the Vera C. Rubin Observatory, which captured pre-discovery images—are racing to study the object before it rounds the Sun and briefly disappears from view in late autumn.