A cosmic growth chart developed by scientists has blended data from the ongoing Sloan Digital Sky Survey with a newfound technique of determining the ages of stars to reach a fascinating conclusion: our Milky Way Galaxy grew from the inside out.
According to Discovery, this conclusion was reached by looking closely at the location and age of the stars in the Milky Way Galaxy. Red giant stars towards the center of the galaxy have been determined to be about 13 billion years old, while younger stars on the fringes of the galaxy are much younger, clocking in at about 1 billion years old.
The news comes out of a meeting of the American Astronomical Society which took place recently in Kissimmee, Florida. It was there that astronomer Melissa Ness, who works with the Max Planck Institute of Astronomy in Heidelberg, Germany, ran through the findings with reporters.
“What we’re able to do… is understand how our galaxy has formed in detail, looking at the dispersion 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.”
Using the Sloan survey spectra to shed light on a star’s chemistry in tandem with optical data based on findings of the Kepler space telescope, the technique Ness is describing is unique in its age-dating technique.
“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,” she said.
Taking advantage of how a star’s mass appears to based on its carbon-nitrogen ratio, a computer model was developed and used to calculate the masses of the 70,000 red giant stars which were observed in Sloan’s APOGEE (Apache Point Observatory Galaxy Evolution Experiment) survey.