Astronomers believe our Milky Way Galaxy formed from the inside out, based on new data from the Gaia-ESO project.
According to a press release, the astronomers can use the data to determine how quickly parts of the galaxy grew. For the study, the researchers tracked magnesium and other rapidly produced elements present in the galaxy.
"The different chemical elements of which stars - and we - are made are created at different rates - some in massive stars which live fast and die young, and others in sun-like stars with more sedate multi-billion-year lifetimes," lead Gaia-ESO Project investigator Gerry Gilmore said in the release.
When a massive star dies, it can create a neutron star or black hole and even lead to the creation of new stars. With typically short lives, they produce large amounts of magnesium in their catastrophic and explosive deaths. The study explains the difference in stellar evolution between the stars toward the center of the Milky Way disc and those farther outside.
"We have been able to shed new light on the timescale of chemical enrichment across the Milky Way disc, showing that outer regions of the disc take a much longer time to form," said study lead author Maria Bergemann, of Cambridge's Institute of Astronomy. "This supports theoretical models for the formation of disc galaxies in the context of Cold Dark Matter cosmology, which predict that galaxy discs grow inside-out."
Stars on the outer part of the Milky Way's disc were younger, about zero to eight billion years old and had less metal. The metal-rich planets were typically older and found closer to the galaxy's center. The older planets were also the larger ones and tended to be more likely to meet their fiery end.
"From what we now know, the Galaxy is not an 'either-or' system. You can find stars of different ages and metal content everywhere," said Bergemann. "There is no clear separation between the thin and thick disc. The proportion of stars with different properties is not the same in both discs - that's how we know these two discs probably exist - but they could have very different origins."
