How far the Milky Way's disk extends has long been difficult to define—it doesn't end sharply, but fades away gradually at its outer edges. Now, for the first time, an international team of astronomers has identified the edge of the Milky Way's star-forming disk by studying the ages of stars, reve aling that the bulk of our galaxy's star formation occurs within 40,000 light-years of the Galactic Center. ...read more read less