How are the Milky Way’s thin disk and thick disk different?

The Milky Way’s disk is composed of two distinct components that differ primarily in their stellar populations and physical characteristics:

• Thin Disk: This is the thinnest component of the Galaxy’s disk. It contains the majority of the Galaxy's gas and dust, as well as its youngest stars.1
• Thick Disk: This component is physically thicker than the thin disk and is distinguished by the presence of somewhat older stars.1

These structural subdivisions are part of a broader classification system used by astronomers to categorize the Galaxy's stellar populations based on age, chemical composition, and kinematics. While the thin disk is associated with more recent star formation, the thick disk represents a population of stars that formed earlier in the Galaxy's history.21