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Scientists Map the Ages of 70,000 Stars—and Confirm How Our Galaxy Grew

ByAllison EckNOVA NextNOVA Next

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In the largest map of its kind, astronomers have confirmed something they knew all along, but couldn’t take for granted: that the Milky Way started as a tiny cluster, and grew outward from there.

The research team amassed data from 70,000 red giant stars across the galaxy and found that the Milky Way’s oldest stars are confined to the center of the galaxy. The team presented

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their findings at the 227 th meeting of the American Astronomical Society.

Leader researcher Melissa Ness of the Max Planck Institute for Astronomy in Germany worked with her colleagues to analyze data from two telescopes. The first was the APOGEE Project , which used a 2.5-meter telescope in Apache Point, New Mexico, to sample the spectra of 300 stars at a time and subsequently determine their chemical composition. Then, they built a model relating a subset of those stars’ color spectra to their mass and age, which had been inferred using Kepler satellite observations.

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In this simulated map of the Milky Way, age is color-coded: the youngest stars are in blue, the oldest stars in red, and middle-aged stars in green.

The creation of a model for star age is a major development in the field of astronomy.

Here’s Jonathan Webb, reporting for the BBC:

“This is somewhat revolutionary because ages have previously been considered very hard to get, particularly from stellar spectra,” Dr. Ness said. “They’re important, but they’re difficult.”

Other techniques for gauging a star’s age, like watching it spin , are much more painstaking.

“This is really the first time that we’ve been able to infer ages for such a large number of stars, rather than relying on this small subset of stars with special observations.”

Someday, this new technique could help astronomers reconstruct the entire galaxy’s formation. The timescale of this evolution, as well as where it happened, could also give scientists further clues as to how stars introduced various elements (through nuclear fusion) to our corner of the universe.

Image credit: M. Ness & G. Stinson / MPIA