Alex Drlica-Wagner

A population census, but instead of houses (galaxies, and instead of residents) stars. Astronomers set out to count the smallest and faintest "homesteads" in our cosmic neighborhood: dwarf galaxies. They are thousands of times fainter than the Milky Way, and spotting them in images is as hard as picking out a firefly in front of a spotlight.

On the outskirts of the Milky Way, tiny stellar systems hide, so faint that even powerful telescopes barely spot them. Until recently, astronomers knew almost nothing about these objects, dubbed ultra-faint compact satellites.

The night sky is like an ocean: the longer you stare, the more faint lights you notice in the depths. That's how astronomers, peering into the outskirts of the Milky Way, found Aquarius IV — a tiny stellar system that had been hiding in the dark until now. The system was spotted in images from an early survey by the future Vera Rubin Observatory.