The European Space Agency (ESA) Euclid space telescope has discovered its first previously unknown comet, named C/2026 S1 (Euclid), located approximately 1.3 billion kilometers from Earth, between the orbits of Jupiter and Saturn, ESA announced on October 19, 2026.
This discovery, made from images taken between September 16 and 24, 2026, is remarkable because Euclid is primarily designed to observe distant galaxies rather than track fast-moving solar system objects such as comets. Mikko Pöntinen of the University of Helsinki and the Euclid consortium’s solar system objects working group used specialized detection software developed by Mikko to identify a “fuzzy streak” across multiple images, characteristic of a rapidly moving object surrounded by a diffuse cloud of dust and gas, indicative of an active comet.
After checking against catalogs of known asteroids and comets, no object matched this observation. The finding was reported to the Minor Planet Center of the International Astronomical Union, which confirmed the cometary nature of the object on October 8.
Located outside the planets’ orbital plane, this comet follows a trajectory passing “above” the solar system and will take several thousand years to complete its orbit. Euclid deliberately avoids regions rich in asteroids and comets to minimize light interference during its deep observations, making this discovery all the more exceptional.
Euclid’s ability to detect comets while they are still distant from the Sun could provide potential targets for ESA’s upcoming Comet Interceptor mission, planned to study little-known comets. Additionally, identifying such moving objects helps eliminate their influence on images intended for Euclid’s primary goal of precise galaxy mapping.
