Red giants map how the Milky Way grew
Measuring the mass of 70,000 aging stars reveals older center, younger outskirts
![red giant](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2016/01/011116_ag_red-giant_free.jpg?fit=860%2C460&ssl=1)
AGE MAP The ages of tens of thousands of red giant stars are charted atop a map of the Milky Way. The oldest stars are in red, near the galactic center. The youngest stars are blue.
M. Ness, G. Stinson/MPIA