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Particles suspended in the atmosphere scatter different wavelengths of sunlight differently. When smoke, dust, or other aerosols are abundant, shorter wavelengths can be scattered away more strongly, leaving more reddish or orange light reaching an observer directly from the Sun. Similar scattering helps produce colorful sunrises and sunsets.
The Sun itself hasn't changed color. What changed is the atmosphere the sunlight had to travel through. Sometimes, unusual skies tell a story about particles that traveled hundreds or even thousands of kilometers.
© NASA Earth Observatory