For the first time, astronomers identify the edge of the Milky Way’s disc
The Milky Way does not come with a clean outer line. Its disc does not stop the way a coastline does. It fades, becoming harder and harder to define as stars grow sparse and the structure stretches into the dark. That uncertainty has made one question especially stubborn for astronomers: where does the galaxy’s star-forming disc actually end? A new analysis points to an answer. By tracing the ages of stars across the Milky Way, an international team of astronomers found that most of the galaxy’s star formation is confined to a region within about 40,000 light-years of the Galactic Centre. Past that point, the pattern of stellar ages shifts in a way that suggests the main star-forming disc has already run out. According to Dr. Karl Fiteni from the University of Insubria, “The extent of the Milky Way’s star-forming disc has long been an open question in Galactic archaeology. By mapping how stellar ages change across the disc, we now have a clear, quantitative answer.” Inside the star-forming disc abundant cold gas fuels star …
