This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The European Space Agency's Euclid space telescope has discovered its first previously unknown comet in images taken between Sept. 16 and 24, 2026. The discovery is impressive for a mission that is designed to take deep, steady images of distant galaxies—not to follow fast-moving solar system objects like comets.
Furthermore, the quick turnaround between identification and validation demonstrates that Euclid can detect new comets while they are still relatively far from the sun, potentially leading to a suitable target for ESA's future Comet Interceptor mission. Mikko Pöntinen of the University of Helsinki, together with the Solar System Objects Science Working Group of the Euclid Consortium, made the initial discovery using moving-object detection software that Pöntinen developed to monitor small solar system objects in Euclid's images. "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." Checks against catalogs of known comets and asteroids found no match, so Pöntinen reported the observations to the International Astronomical Union's Minor Planet Center (MPC) as a new comet. This alerted ground-based astronomers who could then contribute follow-up observations.
The MPC subsequently confirmed it as a comet on Oct. 8, and it is now identified as C/2026 S1 (Euclid). The comet is located approximately 1.3 billion kilometers (810 million miles) away from Earth, equivalent to the distance from the sun to a point roughly between the orbits of Jupiter and Saturn. However, it does not lie in the same horizontal plane as the planets but is currently "straight up" from the sun's perspective, arcing over the solar system on an orbit that will take thousands of years to complete.
Euclid deliberately avoids the asteroid- and comet-rich band of sky along the solar system's plane to reduce unwanted glare from dust that would hinder sensitive deep-sky imaging, making the discovery of new solar system objects particularly challenging. In addition, the telescope's "step-and-stare" imaging strategy typically visits each section of the sky only once, so a comet cannot simply be revisited on demand to confirm its characteristics. Nonetheless, tracking solar system objects is important to correctly identify all objects in the field of view and to remove any "noise"—like moving comet trails or extra light—from Euclid's images that is not relevant to its primary mission of precision galaxy mapping.
"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," says Bruno Altieri, Euclid archive scientist and part of the discovery team. "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," adds Valeria Pettorino, Euclid project scientist.
Extract — continue reading at the source.
