The first complete age map of the Milky Way shows that the galaxy grew from the inside out.
To construct the map, scientists measured the composition and masses of red giant stars to determine their ages. Using a revolutionary technique, the researchers found that older Milky Way stars tend to lie near the center of the spiral galaxy, whereas subsequent generations formed around the spreading edges of the disk.
“This is key to understanding galaxy formation,” Melissa Ness, a postdoctoral student at the Max Planck Institute for Astronomy in Germany, said at a press conference today (Jan. 8) at the 227th Meeting of the American Astronomical Society in Kissimmee, Florida. Ness lead a group that used the Sloan Digital Sky Survey (SDSS) to study the light, or spectra, from red giant stars to produce the first global age map of the Milky Way.
“Measuring the individual ages of stars from their spectra and combining them with chemical information offers the most powerful constraints in the galaxy,” she said.
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