Galaxies To understand the varieties of galaxy types and how they are structured.
Galaxies consist of numerous stars and are held together by gravity.
The factors that determine what type a galaxy becomes are uncertain, but probably include amount of initial rotation and random motions and the interactions with neighbors. Hubble Law and its use Dark Matter problem Properties of galaxy clusters and superclusters. The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy .