When analyzing a galaxy's spectrum, what observation confirms a blue shift compared to laboratory standards?

Answer

The entire pattern of spectral lines is shifted toward the shorter wavelength (bluer) side.

Astronomers compare the observed positions of elemental fingerprints (spectral lines) against known rest-frame positions; a shift toward the blue end signifies motion toward the observer.

When analyzing a galaxy's spectrum, what observation confirms a blue shift compared to laboratory standards?
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