In high-resolution images, what often causes the visible red or pink hues within a star-forming nebula?

Answer

Ionized hydrogen gas energized by powerful ultraviolet light from massive young stars

The red or pink color seen in nebulae is typically ionized hydrogen gas that has been energized by the intense ultraviolet radiation emitted by massive, recently formed O and B type stars.

In high-resolution images, what often causes the visible red or pink hues within a star-forming nebula?
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