Astronomers conducting the Sloan Digital Sky Survey (SDSS) have released a photo of the growth of the Milky Way galaxy, marking the first "growth chart" of its lifespan. The chart utilizes the ages of over 70,000 stars and spans all the way across our galaxy up to 50,000 light-years away, allowing scientists to better understand how the Milky Way grew into the spiral structure that we see today.
"Close to the center of our Galaxy, we see old stars that were formed when it was young and small. Farther out, we see young stars. We conclude that our Galaxy grew up by growing out," Melissa Ness, lead author of the study, said in a press release. "To see this, we needed an age map spanning large distances, and that's what this new discovery gives us."
Using observations gained from red giants, which are bright stars that are at the end of their life, the scientists were able to gather data gained from stars far away from our sun.
"If we know the mass of a red giant star, we know its age by using the fusion clock inside every star," said Marie Martig, co-author of the study. "Finding masses of red giant stars has historically been very difficult, but surveys of the Galaxy have made new, revolutionary techniques possible."
Using data gained from the Apache Point Observatory Galaxy Evolution Experiment (APOGEE), one of SDSS's component surveys, the team was able to obtain high-quality spectra for a large number of stars over a very wide area of the sky. The team believes that in a few years time, it will be possible to obtain data from 70,000 red giant stars with a single telescope.
"In the galaxy we know best - our own - we can clearly read the story of how galaxies form in a Universe with large amounts of cold dark matter," Ness said. "Because we can see so many individual stars in the Milky Way, we can chart its growth in unprecedented detail. This unprecedented, enormous map really is one for the ages."
The findings were presented on Jan. 10 at the American Astronomical Society meeting in Kissimmee, Fla.
