Ursa Major III

[2] It was found by the deep, wide field Ultraviolet Near Infrared Optical Northern Survey (UNIONS), a collaboration between the Canada–France–Hawaii Telescope and Pan-STARRS (two observatories in Hawaii) and spectroscopically confirmed as a real satellite based on data obtained with the Keck Observatory's Deep Imaging Multi-Object Spectrograph (DEIMOS).

Ursa Major III's discovery was announced in November 2023, with a paper appearing in The Astrophysical Journal in January 2024.

This very high value may indicate the presence of a massive dark matter halo, suggesting that Ursa Major III could indeed be a true dwarf galaxy, albeit one with an extremely low stellar mass.

Alternatively, it may be the faintest globular cluster ever discovered, and the observed velocity dispersion could be the product of stellar binarity.

[1] In either case, Ursa Major III / UNIONS 1's total stellar mass is only about 16 M☉, making it the least massive Milky Way satellite known.