The Statement: A star with a greater shift in its spectrum than another star...
... is moving faster relative to us.
Explanation:
* Spectral Shift (Redshift & Blueshift): When a star is moving towards us, the light waves it emits get compressed, shifting the spectrum towards the blue end (blueshift). When a star moves away from us, the light waves stretch out, shifting the spectrum towards the red end (redshift). The amount of shift is directly related to the speed of the star.
* Greater Shift = Greater Speed: A larger spectral shift indicates a faster relative motion of the star.
In Summary: The amount of shift in a star's spectrum provides a direct measurement of its radial velocity (speed towards or away from us).
