First evidence of a globular cluster stream outside our own galaxy

Astronomers have identified the first stellar stream originating from a globular cluster outside of the Milky Way, within the ultra-diffuse galaxy UGC 9050-Dw1. This discovery extends the reach of globular cluster stream analysis to external galaxies, offering a new method to investigate dark matter distribution. Researchers utilized generative stream modelling, directly fitting dynamical models to the stream’s shape, to constrain the mass of the progenitor globular cluster and present the first stream-based halo constraint for an ultra-diffuse galaxy. This work suggests UGC 9050-Dw1 possesses a massive dark matter halo, contributing to the ongoing debate about the composition of ultra-diffuse galaxies. UGC 9050-Dw1, an ultra-diffuse galaxy located 35.2 ± 2 megaparsecs from Earth, exhibits a thin, stream-like feature independently identified in observations using the Hubble Space Telescope and the Canada-France-Hawaii Telescope.…