Overview
- The team identified a thin, arc‑like stellar stream in archival Hubble images of UGC9050‑Dw1 and reported the result in Nature on Aug. 12, 2026.
- Morphology, color and a nearby compact source match expectations for a disrupted globular cluster, and simulated stellar populations reproduce the stream’s observed surface brightness.
- Researchers ran thousands of dynamical simulations and applied generative stream modelling to fit the stream’s shape and constrain the progenitor mass and the host galaxy’s gravitational field.
- The best‑fit models indicate UGC9050‑Dw1 is dominated by dark matter, and the Hubble detection was confirmed with follow‑up ground‑based data as a proof of concept for external galaxies.
- The method opens a new way to map dark matter beyond the Milky Way and could yield many more detections when wide surveys by Euclid and the Nancy Grace Roman Space Telescope begin surveying large sky areas.