Measuring the mass of 70,000 aging stars reveals older center, younger outskirts
M. Ness, G. Stinson/MPIA
KISSIMMEE, Fla. — Our galaxy was built from the inside out. That’s the clear conclusion from an unprecedented survey of the ages of tens of thousands of the galaxy’s stars, reported January 8 at a meeting of the American Astronomical Society. “The Milky Way grew up by growing out,” Melissa Ness, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany, said at a news conference.
Ness and her colleagues developed a computer program that analyzed the light emitted by red giants —bright stars that started out like the sun but exhausted their hydrogen fuel — to determine the stars’ masses and ages. Although scientists were pretty sure that galaxies grow outward, this new census of the galactic interior to the outskirts will help researchers chart that development in impressive detail. “It’s a galactic archaeology project,” says Mario