Euclid Discovers Its First New Comet, C/2026 S1, 1.3 Billion km Away

ESA’s Euclid space telescope has found a comet nobody had seen before, the first time the mission has made such a discovery. ESA announced it on October 19, 2026. The object, now named C/2026 S1 (Euclid), turned up in images taken between September 16 and 24, 2026. The Minor Planet Center, the international clearing house for comet and asteroid observations, confirmed it as a comet on October 8.

The find came from Mikko Pöntinen, a PhD student at the University of Helsinki, working with the Solar System Objects Science Working Group of the Euclid Consortium. He had written software to flag moving objects in Euclid’s images. It marked a streak, the smear left by something moving fast across the field. By predicting where the object would be, he found it in five image sets in the Euclid Deep Field North, 16 exposures in total. A fuzzy cloud around it suggested an active object shedding dust and gas, as a comet does. Checks against catalogs of known comets and asteroids found no match, so he reported it to the Minor Planet Center, which alerted ground-based astronomers to follow up.

The comet is about 1.3 billion kilometers from Earth, roughly between the orbits of Jupiter and Saturn. It sits far above the plane of the planets, on an orbit that will take thousands of years to complete. ESA says the period will be refined as more data arrive.

Why it is a surprise

Euclid is built for deep, steady images of distant galaxies, not for chasing moving objects. It deliberately avoids the dusty band of sky along the Solar System’s plane, and its step-and-stare strategy usually visits each patch of sky only once, so a comet cannot be revisited on demand. Euclid had spotted comets before, but only ones already known.

Tracking such objects still matters for the main goal, which is mapping billions of galaxies to probe dark matter and dark energy: moving trails must be identified and removed from the data. Comets themselves are icy leftovers from the Solar System’s birth about 4.6 billion years ago, so studying them points to the raw ingredients of the planets.

The discovery also worked as a rehearsal. The quick path from detection to confirmation shows Euclid can catch new comets while still far from the Sun, which could someday yield a target for ESA’s future Comet Interceptor mission. Euclid Archive Scientist Bruno Altieri said this comet is not a suitable candidate for Comet Interceptor, but it gives the two mission teams a real test case for coordinating in the future.

More on the mission is in our Euclid hub, and our telescopes and missions guide covers other observatories.