The subtle changes in the color of starlight which let astronomers find planets, measure the speeds of galaxies, and track the expansion of the universe is called: D. Red Shift
An astronomer refers to a scientist or scientific observer who is focused on the study of the celestial bodies outside planet Earth. Some of these celestial bodies include:
A red shift can be defined as a displacement (shift) of the spectral lines of celestial bodies or astronomical objects towards longer wavelengths (the red end of an electromagnetic spectrum), as a result of the Doppler effect.
Hence, a red shift is considered to be a subtle change in the color of visible electromagnetic radiation from stars (starlight), as observed from planet Earth.
Basically, a red shift is used by astronomers in the following ways:
I. For tracking the expansion (increase in size) of the universe.
II. To find a planet.
III. For measuring the speeds of galaxies.
Read more: https://brainly.com/question/17934476
