Redshift - Doppler Effect, Astronomical Applications
source moving closer indicates
A redshift is caused by the Doppler effect, which is the change in wavelength and frequency of either light or sound as the source and observer are moving either closer together or farther apart. In astronomy a redshift indicates that the source is moving away, and a blueshift indicates that the source is moving closer to us. Doppler shifts have many important applications in astronomy. They help us to deduce the masses of stars and of galaxies. The redshifts for the most distant objects in the universe tell us that the universe is expanding.
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Listen to an ambulance or police siren as it passes. You should be able to hear a higher pitch as it is moving toward you and a lower pitch as it moves away. You are hearing the Doppler effect. It works for light as well as sound. The frequency (pitch for sound) and wavelength of both sound and light change if the source is moving relative to the observer. Think of the waves as either being stretc…
How do we actually measure the Doppler shift? When astronomers observe the spectrum of a star or galaxy, they see spectral lines that are produced at specific wavelengths. The wavelengths of these spectral lines are determined by the chemical composition and various physical conditions. The correct wavelengths for spectral lines produced by different elements at rest are measured in laboratories o…
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