The study of the interaction between matter and electromagnetic radiation. In astronomy, it reveals composition, temperature, density, mass, distance, luminosity, and motion by analyzing emitted or absorbed light spectra.
An increase in wavelength of radiation from an object moving away from the observer. The redshift of distant galaxies pr...
A decrease in wavelength and increase in frequency of electromagnetic radiation from an object moving toward the observe...
The change in frequency or wavelength of a wave relative to an observer moving relative to the source. In astronomy, it ...
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