Science For Sleep | UNIONS 1 — The Smallest Galaxy in the Universe

Now on Spotify 🎧 Listen here: https://open.spotify.com/show/033FAXP... Galaxies are usually imagined as enormous cities of stars. Yet UNIONS 1 — the smallest galaxy in the universe reminds us that even the cosmos has its smallest and quietest inhabitants. In this episode, we journey to a tiny galaxy discovered through the Ultraviolet Near Infrared Optical Northern Survey. Despite containing only a modest collection of stars compared to giants like the Milky Way, UNIONS 1 remains a true galaxy—held together by gravity and surrounded by the invisible influence of dark matter. Its existence challenges our understanding of how small a galaxy can be before it ceases to be a galaxy at all. Sometimes, the universe reveals its greatest mysteries not through its largest structures, but through its smallest. Let this gentle exploration of UNIONS 1, the smallest galaxy in the universe settle softly into your thoughts. Breathe slowly. Imagine a faint gathering of stars drifting quietly through the darkness, almost unnoticed among the giants. And rest in the stillness of a universe where even the smallest galaxies have their own place in the cosmic story. Sources: The Discovery of the Faintest Known Milky Way Satellite Using UNIONS — https://arxiv.org/abs/2311.10147 No Observational Evidence for Dark Matter Nor a Large Metallicity Spread in Ursa Major III/UNIONS 1 — https://arxiv.org/abs/2510.02431 Ursa Major III/UNIONS 1: The Darkest Galaxy Ever Discovered? — https://arxiv.org/abs/2311.10134 Reevaluating UMa3/U1: Star Cluster or the Smallest Known Galaxy? — https://arxiv.org/abs/2504.21301 Dark Star Clusters or Ultra-Faint Dwarf Galaxies? Revisiting Ursa Major III/UNIONS 1 — https://arxiv.org/abs/2508.10543