In the context of astronomy, "dropout" typically refers to a type of galaxy that is not observed in certain wavelengths of light, particularly in the ultraviolet or optical bands, but is detected in longer wavelengths such as infrared. This phenomenon is often indicative of high-redshift galaxies, which are many billions of light-years away and play a crucial role in our understanding of the early universe. The term "dropout" is most commonly used in the context of surveys designed to find and study such galaxies.
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