Which galaxy type lacks a definite shape and is often irregular in appearance?

• A. Irregular
• B. Spiral
• C. Elliptical
• D. Lenticular

Answer: (A)

The key idea is galaxy morphology—how galaxies are shaped. Irregular galaxies don’t have a symmetrical, well-defined structure like spirals or ellipticals. Their stars, gas, and dust are distributed in a chaotic, uneven way, often with bright patches of star formation and distorted outlines. This irregular appearance can come from gravitational interactions with other galaxies or from intense internal activity that prevents a smooth, orderly form from developing.

In contrast, spiral galaxies show flat disks with distinct spiral arms and a central bulge, and elliptical galaxies are smooth, rounded ellipsoids with little internal structure. Lenticular galaxies have a disk-like shape but lack spiral arms. Because of these organized shapes, they don’t look irregular in the same way as irregular galaxies do.

So, the galaxy type described as lacking a definite shape and often appearing irregular is the irregular type.