The birth and emergence of our cosmos have been theorized to have grown from the middle, outward. A new galactic map measuring the age of 70,000 stars across the Milky Way confirms this hypothesis, according to a BBC report. Older stars are clustered towards the center of the galaxy’s disc shape, as newer stars trail around the outer ring.
The space map is largest ever assembled presented at the 227th meeting of the American Astronomical Society in Florida. Lead researcher Melissa Ness told the BBC, “We’re characterising in really unprecedented detail how the galaxy is formed, via this snapshot of stellar ages across the disc.” The map’s ringlets extend in different directions: one, threading through the center of the galaxy, and the other extending to outward from the disc. Dr. Ness of the Max Planck Institute for Astronomy in Germany added, “And we not only have these ages in the plane of the disc, but also moving up above the galactic plane.”
The galaxy’s age was determined by collectively measuring data from two telescopes on each star. One of them, the Apogee project, is a derivative of the Sloan Digital Sky Survey, which sampled bands of stars, 300 at a time, using strategic wavelengths. The variation of wavelength’s spectra gave astronomers the chemical composition of the stars but couldn’t tell them their direct age.
So the team sourced the Kepler satellite, which observes stars for an extended timeframe and can establish the mass of each. This model was then extrapolated to calculate the ages of the remaining stars, a particular method which is considered revolutionary. Other techniques, such as watching a star spin, is much more strenuous.
Ness mentions, “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.” She also notes, “These are an extremely valuable star to get ages for, because they are very bright and we see them at very large distances.”
All of this evidence suggests that our galaxy began as a small disc, which grew from the inside out.