First stellar stream found outside Milky Way reveals dark matter clues

Astronomers have detected the first stellar stream from a globular cluster outside the Milky Way, a discovery that could reshape how dark matter is studied in other galaxies. The faint ribbon of stars, named Oyashio, lies in the ultra-diffuse galaxy UGC9050-Dw1, about 115 million light-years away, and was found in archival Hubble Space Telescope data Source: CNN. The finding, published in Nature, marks the first time such a stream has been observed beyond our galaxy Source: infobae.

The discovery

Using images from the Hubble and Canada–France–Hawaii Telescope, researchers led by Julie Kiel Holm of the Niels Bohr Institute identified a thin line of stars stretching about 2,000 light-years, with a width of roughly 72 light-years—similar to Milky Way streams Source: infobae. The stream is the remnant of a globular cluster being torn apart by the galaxy's gravity Source: CNN.

Dark matter implications

Stellar streams have long been used to map dark matter in the Milky Way, but this is the first time the method has been applied to another galaxy. By modeling the stream's shape and motion, the team estimated the galaxy's total mass and its dark matter distribution Source: CNN. "We show that a well-established tool in Milky Way studies can be used to understand other galaxies, where measuring dark matter distribution has traditionally been very difficult," said Holm Source: infobae.

Key points

• The stream is located in an ultra-diffuse galaxy, which may have made it easier to detect Source: CNN.
• The team used a computer program called X-Stream to analyze the data Source: infobae.
• Dark matter is estimated to make up 80–85% of the universe Source: CNN.

Both sources agree on the core facts, though infobae emphasizes the distance as "more than 100 million light-years," while CNN specifies "115 million light-years." The discovery opens a new avenue for probing dark matter in external galaxies.