The stars and gas clouds that orbit in the outer disk are moving faster than they would if the galaxy's mass were concentrated near the __________ of the disk.

Evidence indicates that as much as 90 percent of the galaxy's mass is contained in the _______.

True or False. Around the Milky Way's nuclear bulge and disk is the halo, where the globular clusters are located.

What year did Edwin Hubble invent something?

The question about other objects existing in the sky was answered by Edwin Hubble in 1924. What did he discover in the Great Nebula in the Andromeda constellation?

Mass isn't observed in the form of normal stars, and astronomers hypothesize that some of his unseen matter is in the form of dim ___________, such as white dwarfs, neutron stars, and black holes.

Disklike galaxies with spiral arms are divided into what two subclasses?

The universe began as a fluctuation in a vacuum and expanded very rapidly for a fraction of a second, according to the __________.

What are the three possible outcomes for the universe?