Question

when an object is moving away from an observer, it is said to be

Explanation:

In astronomy, when an object moves away from an observer, the light it emits is stretched, causing a shift towards the red end of the spectrum (longer wavelengths). This is called redshift. When an object moves towards an observer, the light is compressed, shifting towards the blue end (shorter wavelengths), called blueshift.

Answer:

redshifted