A faint ribbon of stars can be seen stretching across the galaxy in the image above. Known as a globular cluster stellar stream, this type of structure preserves clues about its past motion and evolution. By studying these streams, astronomers can learn more about how galaxies developed and how dark matter is distributed within them.
Because these stellar streams respond to gravity, they can act as tracers of dark matter that cannot be seen directly. Until recently, their extreme faintness made them very difficult to detect and analyze. Improvements in massive astronomical datasets and advanced analysis methods are now turning stellar streams into one of the most promising tools for studying galaxies.
First Stellar Stream Found Beyond the Milky Way An international team led by PhD student Julie Kiel Holm of the Niels Bohr Institute and Associate Professor Sarah Pearson of DTU Space has now reported a first-of-its-kind discovery. The results were published in Nature, one of the world's most prestigious scientific journals. "We have discovered a globular cluster stellar stream in another galaxy.
This is the first time such a stream has been observed outside our own galaxy, the Milky Way, which makes the discovery particularly exciting," says Julie Kiel Holm. Finding this kind of structure beyond the Milky Way is especially difficult because the stellar stream itself produces such a weak signal. The newly detected stream is also located inside an ultra-diffuse galaxy, a type of galaxy that gives off very little light.
That combination makes the detection particularly striking. "This opens entirely new possibilities. Not only can we now search for globular cluster stellar streams in other galaxies, but in the long term, we may also be able to measure the dark matter content of more ultra-diffuse galaxies," says co-author Sarah Pearson, who contributed to the discovery during her employment at the Niels Bohr Institute.
What is a globular cluster stellar stream? A globular cluster stellar stream is a long, narrow trail of stars that originated in a globular cluster, a dense collection of stars held together by gravity. These streams develop when the gravity of the surrounding host galaxy gradually pulls stars away from the globular cluster through a process called tidal stripping.
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