Spiral arms are regions of a spiral galaxy that extend from the center and wind outward in a spiral pattern. They are sites of high star formation activity and contain young, hot stars, gas, and dust.
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Spiral arms are primarily found in spiral galaxies, including the Milky Way.
They are formed by density waves that compress gas and trigger star formation.
The Milky Way's major spiral arms include the Perseus Arm, the Carina-Sagittarius Arm, and the Scutum-Centaurus Arm.
Spiral arms are more prominent in grand-design spirals than in flocculent spirals.
Star clusters, nebulae, and molecular clouds are commonly found within spiral arms.