when will a scientist observe redshift in the spectrum of a distant space object?

Question

when the object is moving away from the scientist
when the object is moving toward the scientist
when the object is in the same frame of reference as the scientist
when the object is stationary

Answer 1

A scientist will observe redshift in the spectrum of a distant space object when the object is moving away from the scientist. This is due to the Doppler effect, which causes light waves to appear shifted towards longer wavelengths (redshift) when the source of light is moving away from the observer.