Euclid Space Telescope Discovers Comet C/2026 S1 (Euclidean)

Astronomers have identified a previously unknown comet in images captured by the Euclid space telescope between September 16 and 24, 2026. Officially named C/2026 S1 (Euclidean), the comet was discovered unexpectedly while Euclid was observing distant galaxies.

A distant comet with a thousands-year orbit

C/2026 S1 (Euclidean) is currently about 1.3 billion km (800 million miles) from Earth, roughly the distance between the orbits of Jupiter and Saturn.

The comet is far from Earth’s surface and travels along an orbit that takes thousands of years to complete. Additional observations will help determine its exact orbital period more precisely.

How the comet was discovered

The discovery was made by Dr. Mikko Pontinen, a student at the University of Helsinki and a member of the Solar System Object Science Working Group of the Euclid Consortium.

“I was excited to see that my software detected dirty ‘streaks’ in some images that were the result of fast-moving objects,” Pontinen said.

After predicting the object’s location, the team found it in four additional images, for a total of five image sets.

“By predicting its location, we were able to locate it in other images as well, in a total of five image sets.”

Further examination revealed a hazy cloud surrounding the object. This indicated that it was an active object, such as a comet, emitting dust and gas.

Why Euclid’s comet discovery was unexpected

The discovery is notable because Euclid was designed to study distant galaxies, not to search for objects within our Solar System.

The space telescope also intentionally avoids the dusty bands of sky along the planetary plane, where most comets and asteroids are found. In addition, Euclid typically images each region of the sky only once.

“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 contemporary scans by Euclid resulted in the object being captured in multiple images,” said Euclid Archive Scientist Dr. Bruno Altieri.

Although C/2026 S1 (Euclidean) is not a good candidate for an interceptor mission, its discovery provides a real-world test of how the Euclid mission teams can coordinate in the future.

“Although this particular comet is not a good candidate for an interceptor comet, the discovery and alert process gives us a real test case for how our two mission teams will work together in the future.”

“And of course we are pleased to have discovered a previously unknown comet for the solar system community to follow up on,” added Euclid Project Scientist Dr. Valeria Pettorino.