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Largest Milky Way age map shows how galaxy grew up

"Finding masses of red giant stars has historically been very difficult," said SDSS astronomer Marie Martig.
By Brooks Hays   |   Updated Jan. 12, 2016 at 10:22 AM

KISSIMMEE, Fla., Jan. 12 (UPI) -- An international team of researchers have created the first comprehensive age map of the Milky Way Galaxy.

The map encodes age data from 70,000 stars and encompasses roughly half the galaxy, extending 50,000 light-years across from our solar system. The first map of such magnitude offers a visualization of the galaxy's growth over time.

The map is part of a larger collaborate effort called the Sloan Digital Sky Survey aimed at charting the entirety of the universe. Researchers presented their latest accomplishment last week at the American Astronomical Society meeting in Kissimmee, Fla.

By plotting the age of the Milky Way's stars, astronomers have revealed the trajectory of the galaxy's maturing, showing an outward growth over time.

"Close to the center of our Galaxy, we see old stars that were formed when it was young and small," lead researcher Melissa Ness, a scientist with the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a press release.

"Farther out, we see young stars," Ness continued. "We conclude that our Galaxy grew up by growing out. To see this, we needed an age map spanning large distances, and that's what this new discovery gives us."

Ness and her colleagues were able to date thousands of stars by measuring the masses of red giants. That information allows researchers to decipher the fusion clock inside each star, and work backward to their age.

"Finding masses of red giant stars has historically been very difficult, but surveys of the Galaxy have made new, revolutionary techniques possible," said SDSS astronomer Marie Martig.

The necessary data was collected by the Apache Point Observatory Galaxy Evolution Experiment, called APOGEE, as well as NASA's Kepler mission.

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