Sidney Mau

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.

Astronomers have tested the new Vera C. Rubin telescope in Chile, much like adjusting the focus and aperture on a brand-new camera. The first images covered a patch of sky the size of 60 full Moons, and immediately revealed millions of galaxies and stars. The imaging was done in various colors, from invisible ultraviolet to thermal infrared.

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.