As expected, the analysis shows the galaxy’s central disk formed from the inside out, with red giant stars as old as about 13 billion years clustered toward the center and younger stars about 1 billion years old closer to the disk’s edge, astronomer Melissa Ness, with the Max Planck Institute for Astronomy in Heidelberg, Germany, told reporters at the American Astronomical Society meeting in Kissimmee, Florida.
“What we’re able to do … is understand how our galaxy has formed in detail, looking at the dispersion of ages, the gradient of the ages, how the ages change as a function of both the height from the (disk’s) plane and the radius," Ness said. "It’s understanding the details of this inside-out formation that is now possible."
Unique to the survey is its age-dating technique, which is based on a star’s size. Ness and colleagues used high-quality Sloan survey spectra, which reveals a star’s chemistry, with optical data collected by NASA’s Kepler space telescope to develop a model that can be used to pinpoint a star’s age.
“This is somewhat revolutionary because ages have previously been considered very hard to get, particularly from stellar spectra. They’re important, but they’re difficult,” Ness said.
The key was a newly discovered relationship between a star’s age and its ratio of carbon-to-nitrogen, concentrations of which can be ferreted out by analyzing a star’s spectra.
Read more at Discovery News
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