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How does the Doppler effect shift the spectral lines of approaching and receding stars?
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spectroscopy
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The Doppler effect causes a shift in the spectral lines of stars based on their motion relative to an observer. This phenomenon is a fundamental tool in spectroscopy for determining a star's radial velocity.12
- Approaching Stars: When a star moves toward an observer, the light waves are compressed, resulting in shorter wavelengths. This causes the spectral lines to shift toward the blue end of the electromagnetic spectrum, a process known as a blueshift.31
- Receding Stars: When a star moves away from an observer, the light waves are stretched, resulting in longer wavelengths. This causes the spectral lines to shift toward the red end of the spectrum, a process known as redshift.431
By comparing the observed wavelength of a spectral line to its known wavelength at rest in a laboratory, astronomers can calculate the star's velocity along the line of sight.1