Unbarred spiral galaxy

A spiral galaxy whose disk lacks a prominent elongated stellar bar extending from its center. Its spiral arms emerge from the central region without being anchored at the ends of a bar.

Spiral galaxy: A disk galaxy with spiral arms winding outward from its central region. Unbarred spirals are members of this broader galaxy class.
Density wave theory: A theory that spiral arms are long-lived patterns of enhanced density moving through a galactic disk. It accounts for spiral structure that can exist independently of a stellar bar.
Barred spiral galaxy: A spiral galaxy whose central disk contains a prominent elongated stellar bar. The presence of this central bar is the defining contrast with unbarred spirals.
Andromeda Galaxy: A large spiral galaxy about 2.5 million light-years from the Milky Way. It is commonly classified as an unbarred spiral galaxy.
Galaxy morphology: The classification of galaxies by their shapes and structural features. Morphological schemes distinguish spirals with bars from those without them.
Differential rotation: The rotation of a system at different angular speeds at different radii. It shapes disk structure and winds material around galactic centers.
Lenticular galaxy: A disk galaxy with a central bulge and disk but little visible spiral structure. Its disk lacks the conspicuous arms that distinguish unbarred spirals.
Triangulum Galaxy: A nearby spiral galaxy in the constellation Triangulum, also cataloged as M33. Its lack of a prominent central bar makes it a familiar unbarred example.
Galactic disk: A flattened, rotating region of a galaxy containing stars, gas, and dust. The absence of a prominent bar is judged in the disk's stellar structure.
Swing amplification: A process that amplifies spiral disturbances in a differentially rotating galactic disk. It can strengthen spiral patterns in disks without a prominent bar.

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