Milky Way growth chart reveals how galaxy evolved

Scientists have made a cosmic growth chart of the Milky Way, an innovative blending of data collected by the ongoing Sloan Digital Sky Survey and a new technique to determine the ages of stars.  The analysis shows the galaxy's central disc formed from the inside out, with red giant stars as old as about 13 billion years clustered toward the centre and younger stars about 1 billion years old closer to the disc's edge.