The star is moving toward the earth.
It is due to the phenomenon of the Doppler shift.
The Doppler effect, commonly referred to as "Doppler shift," is the change in the wavelength or frequency of waves as a result of an observer's motion in relation to the wave source.
It is possible to see this apparent wavelength change in the visible light emitted by stars and galaxies.
As a result, a star moving toward Earth appears to emit light with a shorter wavelength than a light source that is stationary. It is known as blueshift because shorter wavelengths cause the spectrum to shift toward the blue end.
While a star traveling away from us appears to shift its light towards longer wavelengths. Astronomers refer to this as redshift since it is closer to the red end of the spectrum.
As the spectrum of a particular star shows the hydrogen line appearing at a shorter wavelength of 480 nm in comparison to the laboratory measurements, that show the same hydrogen lines at a greater wavelength of 500 nanometers, that’s why we conclude that the star is moving toward earth.
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