Emission and reflection nebulae differ primarily in their interactions with light.
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Emission nebulae contain hot gas and dust that emit their own light. This is usually due to the presence of young, hot stars that ionize the surrounding gas, causing it to glow.
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Reflection nebulae, on the other hand, do not emit their own light but instead reflect light from nearby stars, appearing bluish in color due to the scattering of light.
Thus, the correct difference is "interactions with light."