Euclid makes an accidental comet discovery
ESA’s Euclid space telescope is surveying the cosmos, mapping the large-scale structure of the universe in space and time. Its goal is to observe more than 1/3 of the sky, concentrating on how galaxies have evolved over time, in the hopes of providing insight to the nature of dark matter and dark energy. But ESA said on October 19, 2026, that Euclid has made an unexpected discovery, and a first for the space telescope. It spotted a comet some 800 million miles (1.3 billion km) away in our solar system.
The Minor Planet Center named the comet C/2026 S1 (Euclid) in honor of the space telescope. The comet lies somewhere between Jupiter and Saturn’s orbits. Only it’s not in the plane of our solar system with the other planets, asteroids and comets at all. Instead, it’s approximately straight up from the sun’s perspective.
Euclid caught the comet whizzing by background galaxies. Despite its high rate of speed, the comet will still take thousands of years to complete one orbit of the sun.
Finding the streaking fuzzy cloud
Mikko Pöntinen of the University of Helsinki discovered the comet using object-detection software. Pöntinen said:
I was excited to see my software flag a ‘streak’ smeared across several images — the result of a fast-moving object. By predicting its position I could identify it in other images, in total finding it in five image sets. Further inspection revealed that it had a fuzzy cloud around it, indicative of an active object like a comet that is shedding dust and gas.
The space telescope was imaging the Euclid Deep Field North at the time of capture. In the image above, you can see the background galaxies in the field of view as the comet suddenly streaks by. Euclid took those images between September 16 and 24, 2026. The Minor Planet Center confirmed the discovery of the new comet on October 8, 2026.
Euclid intentionally looks away from the solar system’s plane to reduce glare from dust leftover from the creation of planets and asteroids.
Bruno Altieri, Euclid archive scientist and part of the discovery team, said:
Very few comets are expected to be discovered by Euclid so it was a happy coincidence that the combination of the comet’s orbit and Euclid’s scanning over those days captured the object in multiple images.
Finding future targets of the Comet Interceptor
ESA is planning a future mission called Comet Interceptor. The mission will park itself in space and await a target that is not from the plane of our solar system, but one that is pristine and untouched from the outer reaches of the sun’s realm. And now, researchers think Euclid could help Comet Interceptor find a comet to target.
Valeria Pettorino, Euclid project scientist, said:
While this particular comet is not a suitable candidate for Comet Interceptor, the process of discovery and alert gives us a real test case for how our two mission teams will coordinate in the future. And we are of course happy to have discovered a previously unknown comet for the solar system community to follow-up on.
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Bottom line: The Euclid space telescope made an accidental comet discovery as it searched the universe for evidence of dark matter and dark energy. The comet is now named C/2026 S1 (Euclid).
Read more: Euclid finds the most ancient quasars in the universe so far
Read more: New Euclid images reveal hidden gravitational lenses
The post Euclid was mapping the universe. Then it found a comet first appeared on EarthSky.