Natural Sciences Active Updated Aug 25, 2026
A ghostly star stream reveals hidden dark matter around other galaxies
Astronomers found the first stellar stream ever detected outside the Milky Way, a faint trail of stars stripped from a distant galaxy's globular cluster over billions of years. Because the stream traces an orbit shaped purely by its host galaxy's gravity, its shape lets astronomers estimate how much dark matter surrounds that galaxy and how it is distributed, a method long predicted but never before observed elsewhere. The stakes are whether streams like this one turn out to be common enough to map dark matter systematically across many galaxies.
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Aug 25, 2026 Latest
An international team including Northwestern astrophysicist Tjitske Starkenburg and researchers at the University of Copenhagen and the Technical University of Denmark identified the first stellar stream of its kind ever spotted outside the Milky Way, a faint ribbon of stars peeling off a distant galaxy's globular cluster, and used its shape to estimate the galaxy's surrounding dark matter, publishing August 12 in Nature.
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