Galactic ‘Age Map’ helps Astronomers Measure Age of Stars across Milky Way

Largest Galactic ‘Age Map’ helped Astronomers Measure Age of Stars across Milky Way

Astronomers have come up with a largest ever galactic ‘age map’ that measures the age of 70,000 stars across the Milky Way. Presented at the 227th meeting of the American Astronomical Society in Florida, the largest such map ever assembled shows the detailed explanation of how the galaxy is formed through the snapshot of stellar ages across the disc.

Melissa Ness, lead researcher, said in one direction the tendrils of the map extend out from the Earth beyond the centre of the galaxy and in the other direction, the map extends out to the very far reaches of the disc. Dr Ness, who works at the Max Planck Institute for Astronomy in Germany, said the map offers key to understand the galaxy formation. Ness along with the team used the Sloan Digital Sky Survey (SDSS) to study the light, or spectra, from red giant stars to produce the first global age map of the Milky Way. The survey sampled many thousands of stars, 300 at a time, using a wide swathe of wavelengths. The biggest challenge for the astronomers was to determine the mass of such a star, and thus its age. The team then used information collected by the Kepler Satellite to know the mass of the stars.

In order to construct the map, scientists measured the composition and masses of red giant stars to determine their ages. With the help of a revolutionary technique, researchers found that older Milky Way stars tend to lie near the center of the spiral galaxy, whereas subsequent generations formed around the spreading edges of the disk. Astronomers said that sorting the stars in the disc by age helps them to better understand the evolution of the galaxy. Using the SDSS' Apache Point Observatory Galaxy Evolution Experiment (APOGEE), the team targeted 70,000 red giants to determine their ages and locations.

Astronomers said that for the first time they have been able to infer ages for such a large number of stars, rather than relying on this small subset of stars with special observations.