Story perspectives

First globular-cluster stream found beyond Milky Way

8/21/2026

Summary

Story summary

U.S. astrophysicist Tjitske Starkenburg and collaborators discovered a thin stellar stream around galaxy UGC 9050-Dw1.
UGC 9050-Dw1 lies about 115 million light-years from Earth.
The stream is the first known globular-cluster stellar stream identified beyond the Milky Way.
Its shape records the galaxy’s gravitational field, enabling estimates of total mass and dark-matter content.
Computer simulations of globular-cluster disruption matched the observed stream, supporting a massive dark-matter halo.

History

Historical Context

In 1994 Rodrigo Ibáñez’s team identified the Sagittarius stream, revealing the Milky Way’s accretion of dwarf galaxies. The 2006 SDSS-II “Field of Streams” analysis by Vasily Belokurov and Daniel Zucker mapped its split trails, informing halo shape. Following the 2023 Martínez-Delgado survey that catalogued 89 streams in 389 galaxies (?23 %), Tjitske Starkenburg’s Hubble-Gaia study of UGC 9050-Dw1’s thin globular-cluster stream (?107 M?) spurs new NASA/ESO surveys.

1 of 2

Story summary

U.S. astrophysicist Tjitske Starkenburg and collaborators discovered a thin stellar stream around galaxy UGC 9050-Dw1.
UGC 9050-Dw1 lies about 115 million light-years from Earth.
The stream is the first known globular-cluster stellar stream identified beyond the Milky Way.
Its shape records the galaxy’s gravitational field, enabling estimates of total mass and dark-matter content.
Computer simulations of globular-cluster disruption matched the observed stream, supporting a massive dark-matter halo.

1 / 2