Using the doppler effect, astronomers can determine a star’s age and spectrum elements and chemical composition movement toward or away from earth external temperature and source of origin

The answer is; movement toward or away from Earth

Stars that move closer to the observer will be percieved as blue in the electromagnetic spectrum while starts moving away from the observer will appear red and orange. This is what is called the Doppler shift effect. This phenomenon is similar to the higher pitch of the siren of an ambulance approaching you and the low pitch of the siren when the ambulance passes you and is moving away from you.  

Movement toward or away from Earth is the correct answer.

Explanation: