Why do Reflection Nebulae, composed of dust surrounding a star, characteristically appear vividly blue?
Answer
Dust grains scatter shorter, bluer wavelengths of light more efficiently
Reflection Nebulae are formed by dust surrounding a star that is neither hot enough nor dense enough to emit its own visible light. Instead, the light from the nearby star is scattered toward the observer by the interstellar dust grains. This scattering is not uniform across all wavelengths; it is highly dependent on the size of the particles. Shorter wavelengths, corresponding to blue light, are scattered much more effectively by these minute dust grains than longer, redder wavelengths. This preferential scattering causes the nebula to be illuminated with a distinct blue hue, a process related to extinction and reddening.
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