Which type of galaxy lacks a regular shape?

An irregular galaxy is categorized by its lack of a defined shape, which distinguishes it from other types of galaxies. While spiral galaxies have distinct arms and elliptical galaxies have smooth, oval shapes, irregular galaxies appear chaotic in their structure and do not fit into the conventional classifications. This irregularity often results from gravitational interactions, collisions, or recent formation processes that have not yet led to a stable configuration.

The presence of star clusters, gas, dust, and other materials in various arrangements contributes to the irregular appearance. The irregular galaxies can be rich in star formation compared to their more structured counterparts, reflecting their dynamic nature. Understanding this classification helps astronomers in their study of galaxy formation and evolution in the universe.