Euclid discovers its first previously unknown comet
ESA announced C/2026 S1 (Euclid), detected in September images and confirmed on October 8. It is not a target for Comet Interceptor.
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The Euclid space telescope has discovered its first previously unknown comet, C/2026 S1 (Euclid). The European Space Agency announced the result on October 19, 2026. The object was imaged between September 16 and 24 and confirmed as a comet by the International Astronomical Union’s Minor Planet Center on October 8.
University of Helsinki PhD student Mikko Pöntinen identified the moving streak using software that searches Euclid images for small bodies. Further inspection revealed a cloud of gas and dust, indicating cometary activity. The observations comprise 16 exposures in five fields of view.
According to ESA, the comet is approximately 1.3 billion kilometres from Earth. Its orbit passes outside the plane of the planets and takes thousands of years to complete. The precise orbital period will be refined with further observations.
Euclid is primarily designed to map distant galaxies and study the influence of dark matter and dark energy. It has detected comets before, but those were already known. This is the mission’s first discovery of a previously unknown comet.
ESA explicitly states that C/2026 S1 (Euclid) is not a suitable target for the future Comet Interceptor mission. The discovery nevertheless provides a practical test of how the two teams can coordinate to detect and track other distant comets.
Illustrative photograph: Ryan Hutton / Unsplash, Unsplash License. Starry sky, not an image of the new comet or a Euclid observation. Cropped to 1200×675 pixels.
