ESA announces Euclid’s first previously unknown comet discovery

Excitingly, ESA announced on its website on 19 October 2026 that Euclid had discovered its first previously unknown comet.

Mikko Pöntinen, who is affiliated with the University of Helsinki, made the initial discovery. He carried out this work as part of the Solar System Objects Science Working Group of the Euclid Consortium.

The detection software picked out a linear streak across several images, indicating a fast‑moving object. Mikko Pöntinen said he was excited when his software flagged the streak, noting it resulted from a fast‑moving object.

Further inspection showed a fuzzy cloud around the object, indicating an active comet shedding dust and gas.

Checks against catalogues of known comets and asteroids found no match, so Mikko Pöntinen reported the observations to the IAU Minor Planet Center as a new comet. The Minor Planet Center confirmed the object’s cometary nature on 8 October 2026. According to ESA, at the time of discovery the comet was approximately 1.3 billion kilometres away from Earth, a distance roughly equivalent to the region spanning from the Sun past Jupiter to Saturn.

According to ESA, the comet’s orbit is highly inclined, so it does not lie near the plane of the planets. From the Sun’s point of view, the object currently appears positioned straight up. Its orbital period is expected to be on the order of thousands of years.

According to ESA, Euclid points its instruments away from the band of sky where most asteroids and comets reside. This avoidance reduces dust‐glare, thereby improving the quality of its deep‐sky imaging.

According to ESA, Euclid employs a step‐and‐stare observing scheme that visits each patch of sky only a single time, so there is no guaranteed opportunity to re‐observe a comet to confirm its characteristics.

By tracking moving Solar System objects, Euclid can catalogue every source present in its field of view. This process also removes transient features such as comet trails, which would otherwise interfere with the galaxy‐mapping objectives.

Bruno Altieri said the discovery was a happy coincidence, explaining that the coincidence arose because the comet’s orbital path intersected with Euclid’s scanning schedule during the observation period. Valeria Pettorino said the discovery and its associated alert procedure serve as a realistic test case for future mission team coordination, and she added that the astronomical community will be able to conduct follow‐up observations of the newly identified comet.

According to ESA, before this finding, Euclid had observed comets, but all corresponded to already‐known objects. The comet designated C/2026 Esa (Euclid) represents the telescope’s first discovery of an unknown comet.

Comets consist of ice and dust that are remnants from the formation of the Solar System. They formed roughly 4.6 billion years ago. Most comets originate in the Kuiper Belt and the more distant Oort Cloud.

Analyzing cometary composition provides insight into the primitive materials that contributed to planetary formation. Such studies can also reveal information about the delivery of water and organic compounds to early Earth.

Mikko Pöntinen is a PhD student at the University of Helsinki. The discovery was submitted to the Minor Planet Center on behalf of the Solar System Objects Science Working Group of the Euclid Consortium. The collaborating scientists listed in the report are M. Pöntinen, A. A. Nucita, A. Franco, M. Granvik, B. Altieri, S. Kruk, B. Y. Irureta-Goyena and B. Carry.

According to ESA, astronomers discovered the comet in the Euclid Deep Field North. Astronomers recorded the comet’s image in five separate fields of view spanning several observation days. Each field received between two and four individual exposures. These observations totaled 16 exposures.

The Minor Planet Center of the International Astronomical Union functions as the worldwide clearing house for comet and asteroid observations. It gathers reports from observers across the globe. Researchers use these data to verify new discoveries, determine orbital parameters and assign formal designations.

Scientists will refine the orbital period of C/2026 Esa (Euclid) once they have collected more data. The interval between the comet’s initial detection and its formal validation was short. This rapid turnaround demonstrates that Euclid is capable of discovering new comets even when they remain distant from the Sun.

Euclid’s mission aims to take deep, steady images of distant galaxies. Euclid was not intended to track fast-moving Solar System objects such as comets. This capability could lead to a suitable target for ESA’s future Comet Interceptor mission.

The Euclid mission seeks to uncover how dark matter and dark energy shape the observable Universe. During its planned six‐year operational lifetime, the telescope will measure the shapes and motions of billions of galaxies extending out to 10 billion light‐years.