A European spacecraft built to map galaxies has discovered a new comet serendipitously, proving it can do more than study dark matter and dark energy in the distant universe.

The Euclid Space Telescope spotted the space snowball, dubbed C/2026 S1 (Euclid) between Sept. 16 and 24, after the renegade had smudged five image sets.

The European Space Agency's mission, launched in 2023, takes long exposures of faraway galaxies, not high-speed photography of zippy objects in our own solar system. But moving-object software, developed by Mikko Pöntinen, a doctoral student at the University of Helsinki, flagged an errant streak. Finding and removing stray signals is crucial for the mission to photograph about one-third of the entire sky in every direction around Earth.

"By predicting [the object's] position, I could identify it in other images," Pöntinen said in a statement .…