What causes the bluish color often seen in the spiral arms of spiral galaxies?

Answer

They contain many young, hot, luminous stars

The spiral arms are active sites of star formation, meaning they are populated by many newly formed stars that are hot and luminous, giving those regions a bluish appearance.

What causes the bluish color often seen in the spiral arms of spiral galaxies?

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Types of Galaxies in Space - Spiral, Elliptical, Irregular plus more

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