Euclid space telescope captures new comet C/2026 S1

About 40 to 70 new comets are discovered every year, but C/2026 S1 (Euclid) stands apart because it was found entirely by accident by a European Space Agency telescope that was looking away from the ecliptic plane. Located roughly 1.3 billion kilometers (or 800 million miles) away from Earth—a span matching the distance between the sun and the orbits of Jupiter and Saturn—the object was spotted by the Euclid space telescope while researchers focused on capturing deep-space images of distant galaxies.

The Tech TL;DR:

• The Discovery: Spotted on September 17, 2026, by custom object-detection software written by Mikko Pöntinen of the University of Helsinki.
• The Trajectory: Originating from the Oort Cloud, the long-period comet travels on an unusual orbital path high above the solar system before its upcoming perihelion in 2027.
• The Architecture: Found thanks to Euclid’s deep field survey and its step-and-stare mapping method, which occasionally revisits specific extragalactic sky coordinates.

Euclid Telescope Captures Accidental Comet Images

The European Space Agency launched the Euclid space telescope to map the large-scale structure of the universe, focusing on dark matter and dark energy by observing more than one-third of the extragalactic sky. The telescope captured the accidental comet images at 00:41:07, 00:58:53, and 01:16:39 UTC on September 17, 2026. Rather than hunting for solar system bodies, the Solar System Objects Science Working Group deliberately pointed the instrument away from the ecliptic plane—the crowded band where most planets, asteroids, and standard comets reside—to minimize interference from cosmic dust.

Despite that careful positioning, the comet zipped through the field of view. Mikko Pöntinen caught the object using automated object-detection software designed to flag movement. I was excited to see my software flag a ‘streak’ smeared across several images, Pöntinen said in a statement. Further inspection by Pöntinen revealed a fuzzy cloud surrounding the streak, confirming an active object shedding dust and gas.

Data Collection and Orbital Mechanics of C/2026 S1

Because Euclid employs a step-and-stare method—holding a single gaze on a target coordinate for roughly an hour before moving on—most parts of the sky are imaged only once during its wide survey. However, the telescope also conducts periodic deep field surveys, revisiting select coordinates a handful of times per year. Those repeat glimpses made the identification of C/2026 S1 (Euclid) possible.

This discovery is indeed a happy coincidence as few comets are expected to be discovered by Euclid, Bruno Altieri, archive scientist and member of the Euclid solar system team, said. Valeria Pettorino, Euclid project scientist, noted that the event serves as a practical test case for coordination between mission teams, even though the trajectory makes this particular object unsuitable for missions like Comet Interceptor.

Astronomers have classified C/2026 S1 (Euclid) as a long-period comet with an orbit exceeding 200 years. Altieri stated that the object almost certainly originated in the distant Oort Cloud, a shell of icy bodies and planetesimals surrounding the solar system. The comet’s trajectory approaches from far above the plane of the planets, cutting between Saturn and Jupiter. The Minor Planet Center officially designated the object following calculations of its speed and trajectory across five image sets.

Timeline for Perihelion and Ongoing Observations

Very little data has been gathered so far because the telescope has only imaged the object a few times. The comet is currently positioned at the upper end of its sweeping orbit and is expected to reach perihelion—its closest approach to the sun—in 2027. Following that close pass, the object will take thousands of years to complete its full cycle and return to the inner solar system.