Light Emission: Explaining Discrepancy using Doppler Effect

The problem below is similar to the problems in chapters 25 & 26 in the Cutnell and Johnson College Physics book so it should be solved in a similar fashion. This is physics-II without calculus:

An astronomer is making an observation of a new discovered galactic object. Part of this observation is the analyisis of the light emitted by the object. It is observed that this light includes a clear pattern of the emission spectrum of atomic hydrogen. Part of that spectrum is the H-sub:alpha line, which on earth has a wavelength of 656.258nm (10^-9m). The light from this object has this spectral line at 659.0nm. Explain this discrepancy, quantitatively, using the Doppler effect.

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...e length of 659.0 nm. This discrepancy (technically known as Doppler effect) is due to the recession of the galaxy away from the earth. As per the big bang theory of the origin of the universe, ...