Question

how is red shift helpful in astrophysics??

Answer 1

Red Shift helps us to know if an object is relatively moving away from us or not, possibly due to the expansion of the universe. If the light coming from an object is redshifted then it is moving away, else it is not.

Answer 2

redshifts and blue shifts describes how light changes as object in space move closer or farther away from us the concept is a key to charting universe's expansion .
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.hope this may help you