- A faint stellar stream was found outside the Milky Way in archival Hubble data
- The stream is in galaxy UGC 9050-Dw1, about 115 million light-years from Earth
- Researchers used the stream to map the galaxy's gravitational field and total mass
A faint trail of stars in a distant galaxy has helped astronomers uncover a discovery that could provide new clues about dark matter and how galaxies form and evolve. Researchers found the barely visible stellar trail in archival data from the Hubble Space Telescope. It is the first globular cluster stellar stream detected outside the Milky Way. The stream is located in a galaxy around 115 million light-years from Earth and is the remains of a dense group of stars being slowly pulled apart by the gravity of its host galaxy, reported CNN.
When stars gradually break away from a star cluster, the remaining stars form a long, thin stellar stream. Astronomers have discovered dozens of such stellar streams in the Milky Way, but many remain undetected due to their extremely faint light.
Details of this discovery were published in a study in the journal Nature. Modeling the stellar stream helped scientists map the galaxy named UGC 9050-Dw1 and study its gravitational field.
A galaxy's gravity influences the shape and motion of a stellar stream. Based on this, researchers studied the galaxy's gravitational field and estimated its total mass, which included both visible matter-such as stars-and dark matter.
Co-lead author Julie Kiel Holm described the realisation that they had found a stellar stream outside the Milky Way as "very exciting."
She noted that the team then began considering the possibilities for further research.
The true nature of dark matter remains a mystery to scientists. Although it cannot be observed directly, its gravitational effects on stars and galaxies are detectable.
According to Kiel Holm, scientists estimate that dark matter makes up about 80 to 85 percent of the universe, therefore, efforts to understand it are crucial.
Scientists have previously used stellar streams to study dark matter within the Milky Way. Now, this new discovery offers the potential to apply the same technique to better understand the quantity and structure of dark matter in other galaxies.
This new stellar stream was found in an "ultra-diffuse galaxy," which is characterised by very low luminosity and a highly spread-out structure.
Researchers believe these characteristics may have made it easier to identify the stellar stream.
Co-lead author Sarah Pearson explained that ultra-diffuse galaxies are considered quite massive. She stated that a galaxy needs to be sufficiently massive to pull stars from its original star cluster.
