Which major parts make up the Milky Way Galaxy’s structure?

The structure of the Milky Way Galaxy is characteristic of a large spiral system and is composed of six distinct, often overlapping parts:1

• Nucleus: Located at the very center, this region contains a massive black hole known as Sagittarius A*, which is surrounded by a rotating accretion disk of high-temperature gas.2
• Central Bulge: A dense region surrounding the nucleus.1
• Disk: Comprising both a thin and a thick disk, this component contains the majority of the galaxy's stars.1
• Spiral Arms: These structures, which follow a logarithmic spiral pattern, are regions of density enhancement where stars and gas clouds are concentrated.13
• Spherical Component: A structural element that contributes to the galaxy's overall shape.1
• Massive Halo: A nearly spherical volume that surrounds the galaxy, containing thinly scattered stars, globular clusters, and tenuous gas.14

Much of the galaxy's structure is obscured from optical view by interstellar dust, requiring astronomers to use radio and infrared telescopes for detailed study.5