A team of astronomers from the Sloan Digital Sky Survey (SDSS) has presented at the meeting of the American Astronomical Society the first ‘growth curve’ of our galaxy, the Milky Way, that is, a map that helps us to visualize how our galaxy has grown from its youngest times to the mature spiral galaxy that it is today.
Scientists, led by Melissa Ness, from the Max Planck Institute for Astronomy in Heidelberg (Germany), have used the ages of more than 70,000 red giant stars (which can be observed at great distances from our Sun), extending up to half from our galaxy 50,000 light years away.
By knowing the mass of a red giant, astronomers can find out its age using the internal fusion clock that all stars possess. “Finding masses of red giant stars has historically been very difficult, but investigations of the galaxy have made possible revolutionary new techniques,” explains Marie Marting, co-author of the study.
Thanks to this age map (built using APOGEE observations previously captured by the Kepler telescope) in which we can see near the center of the galaxy old stars formed when it was very young and, much further away, young stars, astronomers have found that the Milky Way grew by expansion.
These more than 70,000 red giants were sampled throughout the galaxy: “In the galaxy we know best – ours – we can clearly read the history of how galaxies form in a universe with large amounts of cold dark matter . Since we can see so many individual stars in the Milky Way, we can trace their growth in unprecedented detail. It is thus a huge age map never seen before ”, clarifies Ness, leader of the work.
Image Credit: G. Stinson (MPIA)
