What physical feature forms the unique spectral fingerprint analyzed by astronomers?
Answer
Dark, fine absorption lines caused by cooler outer atmospheric gases.
The unique spectral fingerprint used for precise measurement consists of dark, fine lines superimposed on the continuous spectrum, known as absorption lines. These lines arise because specific elements, such as hydrogen or helium, present in the star's cooler outer atmosphere absorb light energy only at very specific wavelengths corresponding to their unique energy transitions. Since the exact wavelength of every spectral line for a known element is cataloged accurately in laboratory settings on Earth, any shift in the observed pattern from these known locations reveals motion.
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