A team of researchers identified the outermost edge of the Milky Way galaxy. Using the Subaru Telescope, the researchers examined the boundary of the stellar system that makes up the galaxy. The ultimate size of the galaxy is 520,000 light years in radius, 20 times larger than the distance between the galactic center and our solar system (26,000 light years) (Figure 1). Stars that reach these outermost regions of the galaxy during their orbital motions are ancient stellar populations with ages as old as 12 billion years. The spatial extent in which these ancient stars wander is, therefore, important for understanding the Milky Way's formation.
