This is interesting that they may believe that the Milky Way grew inside out. If this true, I wonder if any other or even all spiral galaxies grew similar.
QuoteA breakthrough using data from the Gaia-ESO project has provided evidence backing up theoretically predicted divisions in the chemical composition of the stars that make up the Milky Way's disc – the vast collection of giant gas clouds and billions of stars that give our Galaxy its 'flying saucer' shape.
http://phys.org/news/2014-01-milky-insi ... actic.html (http://phys.org/news/2014-01-milky-inside-out-gaia-insight-galactic.html)