On July 1, 2025, a telescope perched in the Chilean Andes caught sight of something extraordinary: a comet from another star system. Now officially named 3I/ATLAS, this icy traveler is only the third confirmed interstellar object ever observed, following the enigmatic ‘Oumuamua in 2017 and comet 2I/Borisov in 2019.
The NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) telescope in Rio Hurtado first spotted the object streaking in from the direction of the constellation Sagittarius. At the time, it was about 420 million miles (670 million km) from Earth, roughly the distance to Jupiter, and moving at a blistering 152,000 mph (245,000 km/h).
But this wasn’t a sudden appearance. After the initial detection, astronomers dug into archival data from ATLAS telescopes and the Zwicky Transient Facility in California, uncovering pre-discovery images dating back to June 14. These early glimpses helped confirm the comet’s hyperbolic trajectory, a telltale sign that it’s not bound by the Sun’s gravity and is simply passing through.
What makes 3I/ATLAS so exciting isn’t just its speed or rarity; it’s what it might be made of. As a comet, it carries ice, dust, and gas from a completely different star system. Studying it could offer clues about how planets form elsewhere in the galaxy, or even hint at the building blocks of life beyond Earth.
“These things take millions of years to go from one stellar neighborhood to another,” said Paul Chodas, director of NASA’s Center for Near-Earth Object Studies.
Despite its dramatic entrance, 3I/ATLAS poses no threat to Earth. It will stay at least 1.6 astronomical units (about 150 million miles) away. Its closest approach to the Sun — 1.4 AU, just inside Mars’ orbit, will happen around October 30.
The comet is expected to remain visible to ground-based telescopes through September, after which it will disappear behind the Sun’s glare. It should reemerge in early December, offering astronomers another chance to study it before it vanishes into the cosmic dark.
With only two other interstellar objects ever observed, 3I/ATLAS is a scientific jackpot. Telescopes around the world, including the James Webb Space Telescope and the upcoming Vera C. Rubin Observatory, are racing to gather data before it’s gone.
