Overview
- An international team used data from the LAMOST and APOGEE spectroscopic surveys and ESA’s Gaia mission to map stellar ages and locate the boundary about 11.3–12.2 kiloparsecs from the Galactic Center.
- The team identified a U-shaped age pattern with the youngest stars at the cutoff and older stars both inside and beyond it, marking where new stars largely stop forming.
- Stars found past the edge are mostly older migrants that drifted outward over time through interactions with spiral arms, and their near-circular orbits point to in-disk origins rather than kicks from past collisions.
- Supercomputer simulations reproduced the U-shaped profile and indicate a steep drop in star-formation efficiency defines the outer limit of the star-forming disk.
- The physical cause of the cutoff remains unsettled, with ideas ranging from the bar’s Outer Lindblad Resonance to the Galaxy’s warp or low gas density, and upcoming 4MOST and WEAVE surveys are expected to refine the picture.