This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The Milky Way is home to hundreds of billions of stars arranged in a glorious spiral pattern. But beyond the obvious spiral, our galaxy has other physical characteristics.
It's divided into a galactic bulge, a galactic disk and a galactic halo. The disk is further divided into a thin disk and a thick disk. They're not only structurally different, but their stellar populations and other characteristics are different.
The thin disk contains young stars and middle-aged stars like our sun. It holds the spiral arms, where our solar system resides, and most of the Milky Way's gas and dust. It's also where young stars form.
It has higher metallicity, generated by previous generations of stars that have lived and died. The thick disk is puffier and more diffuse than the thin disk. It holds ancient stars, and almost no new stars form there.
It has much lower metallicity than the thin disk, and astronomers sometimes refer to it as a kind of stellar fossil record. Astronomers wrestle with understanding the formation of these disks and the Milky Way as a whole. Observations have led to multiple explanations.
In one, stars are born in the thin disk, and over time, encounters with gas clouds, the spiral arms or even the central bar perturb some of these stars. Dynamical scattering drives them away from the plane of the thin disk. Another explanation says that as stars form in the inner disk, the gas they form from settles down into an even thinner disk.
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