The Comet From Another Star

The Comet From Another Star By Mark Thompson - March 01, 2026 11:13 PM UTC | Planetary Science Something arrived in our Solar System last summer that had been travelling for longer than the Earth has existed. It came from somewhere out there in the dark between the stars, possibly from a planetary system that formed billions of years before our own Sun even ignited. We don't know exactly where it came from. We may never know. But for a brief, extraordinary window of time, this ancient wanderer passed close enough to study, and the world's astronomers dropped almost everything to watch. Its name is 3I/ATLAS. The numbers and letters tell you it's the third interstellar object ever detected, and it was spotted by the ATLAS survey telescope in Chile, a network of instruments designed to scan the night sky for objects that might one day threaten Earth. What it found instead was something that posed no threat whatsoever, but was infinitely more exciting. A comet, travelling at over 240,000 km per hour, on a trajectory that no object born in our own Solar System could ever follow. It had come from somewhere else entirely. Evolution of 3I/ATLAS as seen by the Vera C. Rubin Observatory's LSSTCam during science validation observations. The four inset images show the comet on 21 June 2025 (ten days before discovery), 2 July, 3 July, and 19 July 2025. The upper portion shows the comet's trajectory through the inner Solar System (Credit : NSF–DOE Vera C. Rubin Observatory) In the months that followed, a scramble of observations took place. Hubble photographed it. X-ray telescopes caught it glowing in high energy light. NASA's Parker Solar Probe watched it race around the Sun. Infrared observatories detected organic molecules and water vapour streaming off its ancient surface. One researcher described the experience as being like glimpsing a rifle bullet for a thousandth of a second, over before you can quite comprehend what you've seen. But one of the most remarkable images has ...