Starbirth shuts down 40,000 light-years from the Milky Way's core — and astronomers don't know why

Astronomers have found the boundary of star formation in the Milky Way's spiral disk — and it's not as far out from the center of our galaxy as you might imagine. The Milky Way is at least 100,000 light-years across, but the new results suggest that the galaxy's star formation takes place within a region that extends to a radius of 40,000 light-years from the galactic center. …