The observation by Hubble that demonstrated for the first time that the Andromeda "nebula" was at a very large distance from the Sun and outside the Milky Way Galaxy was that
A) Cepheid variable stars appeared to be very faint in the "nebula."
B) the "nebula" appeared to be rotating night by night around a center that was not the center of the Milky Way.
C) stars with characteristics similar to those of the Sun appeared to be absent in the "nebula."
D) globular clusters appeared to be distributed in a halo around the "nebula," a sure sign of a separate galaxy.

Question

Quizplus · Accepted Answer

Hubble's observation of Cepheid variable stars in the Andromeda "nebula" being very faint indicated that these stars were at a much greater distance than previously thought, leading to the conclusion that Andromeda was outside the Milky Way Galaxy.

The Observation by Hubble That Demonstrated for the First Time