The European Space Agency’s Euclid Mission is mapping the distribution of galaxies on large scales with the intention of finding out about the nature of dark matter and dark energy. Making such maps involves surveying large areas of the sky for a very long time and doing that makes it inevitable that something unexpected will crop up. That happened last month, between 16th and 24th September 2026, when the Euclid telescope accidentally discovered a comet.
Here is an image showing what Euclid was looking at when the comet intruded:

Here is is a comparison of frames showing the motion of the comet, which is easily identifiable by the large arrow pointing at it together with the word “comet”.

The serendipitous comet is named C/2026 S1 (Euclid) – and, before you ask, no it’s not an alien spacecraft.
