Which dense gas region spans the center of the Milky Way?

The Central Molecular Zone is the dense gas region that spans the center of the Milky Way. Astronomers use the name for the inner region filled with giant molecular clouds and unusually concentrated molecular gas.

It lies around the Galactic Center, in the direction of Sagittarius, and contains objects such as Sagittarius B2, one of the galaxy’s best-known star-forming molecular-cloud complexes. The zone is not a sharply edged sphere; it is a dynamic, asymmetric structure shaped by the Milky Way’s central gravitational environment.

Compared with molecular clouds elsewhere in the galactic disk, gas in the Central Molecular Zone is generally denser, warmer and more turbulent. It also experiences stronger radiation and cosmic-ray activity. These conditions make it an important laboratory for studying how stars form under extreme conditions.

The Central Molecular Zone is different from the Oort Cloud and Kuiper Belt, which are Solar System structures. It is also much more concentrated than the Local Bubble, the lower-density cavity surrounding the Sun.