The Hubble law is one of the most important relations in modern astronomy because it ____.
A) allows astronomers to measure the distance to very distant galaxies using only their spectrum
B) explains the difference in the types of galaxies seen in different directions
C) relates the rotation curve of a galaxy to the amount of dark matter it contains
D) connects the mass of a spiral galaxy's bulge to the size of its central black hole
E) determines the mass of a cluster using the rotation period of the galaxies it contains

Question

Quizplus · Accepted Answer

The Hubble law, which relates the redshift of a galaxy to its distance from us, allows astronomers to measure the distance to very distant galaxies using only their spectrum. This is because the redshift is proportional to the galaxy's velocity away from us, which, according to Hubble's law, is directly related to its distance.

The Hubble Law Is One of the Most Important Relations