What does it mean when an emission line of helium from a galaxy is shifted towards red.

A the galaxy contains a small percent of hydrogen
B the galaxy is moving toward the viewer
C the galaxy is moving away from the viewer
D the galaxy contains a large percent of hydrogen

1 answer

When an emission line of helium from a galaxy is shifted towards the red part of the spectrum, it indicates a "redshift." This typically means that the galaxy is moving away from the viewer.

Therefore, the correct answer is:

C the galaxy is moving away from the viewer.