Astronomers have known that galaxies are separate entities outside of our own for roughly the last
A) 35 years.
B) 60 years.
C) 90 years.
D) 150 years.
E) 210 years.

Question

Quizplus · Accepted Answer

Astronomers have known that galaxies are separate entities outside of our own for roughly the last 90 years, since Edwin Hubble's observations in the 1920s confirmed that the Andromeda "nebula" was actually a separate galaxy.

Astronomers Have Known That Galaxies Are Separate Entities Outside of Our