Astronomers have located the edge of the Milky Way’s star-forming disk for the first time, showing that star formation is focused within 40,000 light-years of our galactic center. An artist's illustration of the Milky Way's warped stellar disk, based on Gaia data. Stefan Payne-Wardenaar; Magellanic Clouds: Robert Gendler / ESO Disk galaxies like the Milky Way form stars “inside-out” — starting from the center and working outwards through the disk. So, as a general rule, the farther out astronomers look, the younger the stars are. Now, a team led by Karl Fiteni (then at University of Malta), carried out under the supervision of Joseph Caruana and Victor Debattista, has analyzed more than 100,000 giant stars. By coupling observations with advanced computer simulations, the astronomers show that this inside-out pattern reverses at between 35,000 and 40,000 light-years from the Milky Way’s center. Beyond this distance, the stars are older again.…