Milky Way disk grew upside down with younger stars in thinner layers
Astronomers report that the Milky Way's galactic disk formed with younger stars appearing in increasingly thin layers over time.
Galaxy structure and composition
The galaxy consists of a bulge, a halo, and a disk divided into thin and thick parts. The thin disk holds young stars like the sun along with most of the gas and dust. It possesses higher metallicity because previous generations of stars lived and died within it.
Formation process details
The thick disk is puffier and contains ancient stars where almost no new stars form today. This region has much lower metallicity compared to the thin disk and acts as a stellar fossil record. Scientists are still debating how these distinct layers developed during the galaxy's history.
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