Why do Reflection Nebulae often appear blue when illuminated?
Answer
Shorter wavelengths (blue) are scattered more efficiently by dust.
Reflection Nebulae do not emit their own light but instead scatter light from nearby stars that are not hot enough to cause ionization. The dust particles within these clouds are highly effective at scattering shorter wavelengths of light, which corresponds to the blue end of the visible spectrum. This preferential scattering mechanism is analogous to why Earth's atmosphere appears blue, as the fine particles redirect blue light more readily toward an observer than longer, redder wavelengths.
#Videos
Nebulae: Crash Course Astronomy #36 - YouTube
Types of Nebulae - Clouds of Gas and Dust - YouTube
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