On 1 July 2025, a planetary-defence telescope in Chile built to spot dangerous asteroids found something far rarer: 3I/ATLAS, a comet arriving from interstellar space and only the third such object ever confirmed. When discovered inside Jupiter’s orbit, it was racing through the solar system at 137,000 miles per hour.

On 1 July 2025, a planetary-defence telescope in Chile built to spot dangerous asteroids found something far rarer: 3I/ATLAS, a comet arriving from interstellar space and only the third such object ever confirmed. When discovered inside Jupiter’s orbit, it was racing through the solar system at 137,000 miles per hour.

The first images did not look like the arrival of a messenger from another planetary system. They showed a faint point of light shifting through a dense field of stars, exactly the sort of modest clue on which much of observational astronomy depends. That point was recorded by a telescope at Río Hurtado in Chile and reported on 1 July 2025. The telescope belonged to ATLAS, the Asteroid Terrestrial-impact Last Alert System, a NASA-funded network …