Milky Way's star-forming disk ends at 40,000 light-years from the center, baffling astronomers
Astronomers mapped the Milky Way’s star-forming disk and find that active star formation ends at roughly 40,000 light-years from the center; the Sun sits well inside this boundary at about 26,000 ly. The stellar age distribution forms a U shape—young toward the center and older beyond the edge due to radial migration where stars born closer in travel outward along spiral arms. Simulations suggest a sharp drop in star-formation efficiency at 40,000 ly, potentially linked to the Galaxy’s bar or disk warp. The finding relies on Gaia data plus ground-based spectroscopy from LAMOST and APOGEE and is published in Astronomy & Astrophysics.
