AS 101 - September 15, 2011
Galaxy: A large group of stars in space, all held together by gravity and orbiting a
common center. 100 billion stars are in the Milky Way galaxy.
Nebula: An interstellar cloud of gas and/or dust.
Cluster: A group of galaxies all held together by gravity. The Milky Way galaxy is
part of the Local cluster.
Supercluster: A concentration of clusters. The Local cluster is part of the Local
supercluster. Superclusters form filaments and walls around voids. These are the
largest known structures in the