Smear

Euclid is built to hold still and look a long way past us. It keeps its back to the flat of the planets, where the dust and the glare are, and visits each patch of sky once.

In the third week of September something crossed five of those patches and left a streak in the frames, a mark the galaxy map would rather not carry.

There is software for things that move, partly to know them, partly to take them out so the galaxies stay clean. Mikko Pöntinen wrote it. It flagged the streak. He guessed where it would be in the next set, and it was there, with a soft edge, dust and gas coming off.

No catalog had it. It's past Jupiter's distance, but straight up from the sun, going over the whole flat business on a loop of thousands of years.

Its name now is C/2026 S1 (Euclid), after the eye that was trying not to see it.