Stellar stream discovery beyond Milky Way helps map dark matter

Key Points:

• Astronomers discovered the first globular cluster stellar stream outside the Milky Way using archival data from the Hubble Space Telescope, located in the ultra-diffuse galaxy UGC 9050-Dw1 about 115 million light-years away.
• This faint trail of stars, formed as a dense star cluster is pulled apart by its host galaxy's gravity, allows researchers to map the galaxy’s gravitational field and estimate its total mass, including its dark matter content.
• Stellar streams have been used to study dark matter within our galaxy, and this discovery suggests similar methods can now be applied to other galaxies, potentially advancing understanding of galaxy formation and dark matter distribution across the universe.
• The detection was facilitated by the ultra-diffuse nature of the host galaxy, which provided a faint background and strong tidal forces to reveal the stream, and future telescopes like NASA’s Nancy Grace Roman Space Telescope are expected to aid in finding more such streams.
• Observing stellar streams beyond the Local Group offers new opportunities to study galactic evolution and the elusive nature of dark matter, with features like gaps in streams potentially indicating interactions with dark matter concentrations.