A faint ribbon of stars in a distant galaxy has led astronomers to a discovery that could reveal secrets about one of our universe’s greatest mysteries.
Hidden within the Hubble Space Telescope’s archival data, researchers found the barely visible trail of stars — the first globular cluster stellar stream detected outside the Milky Way. The celestial phenomenon, located in a galaxy roughly 115 million light-years from Earth, is the remnant of a dense ball of stars being slowly pulled apart by the gravity of its host galaxy. As the cluster loses stars, the remnants form a long, narrow stream.
Astronomers have found dozens of stellar streams within the Milky Way, but because these trails are faint and hard to detect, many more are likely left to be discovered. Now, with evidence that they occur in other galaxies, astronomers may be able to use them as cosmic tracers to understand better how galaxies form and evolve.
The finding, which was detailed in a study published Wednesday in the journal Nature, also allowed the team of astronomers to map the galaxy — known as UGC 9050-Dw1 — and its gravitational field by modeling the stream.
Because the galaxy’s gravity influences the stellar stream’s shape and motion, the researchers used the trail of stars to trace the galaxy’s gravitational field. Through their modeling, they were also able to estimate the galaxy’s total mass, how much of it is made up of visible objects, such as stars, and how much is composed of dark matter — a mysterious form of matter that cannot be seen but has gravity.
