A galaxy is a massive ensemble of hundreds of millions of stars and planets, all interacting through the gravitational force, orbiting around a common center. The universe contains hundreds of millions of galaxies. Some scholars theorize that the center of every galaxy lies a super massive black hole.
Young Earth Creationism View
Young earth creationist scientist assert that materialistic explanations of galaxy formation are unsupportable and counter evidence.   In 1988, fifty cosmologists attended a conference which focused on galaxy formation. After summarizing the observational data, two of the most respected scientists estimated the probability that any existing theory on galaxy formation is correct was about 1 out of 100.  In 1999, J. Bland-Hawthorn wrote in the science journal Nature the following:
In 1977, Stephen Weinberg observed that "the theory of the formation of galaxies is one of the great outstanding problems of astrophysics, a problem that today seems far from solution". Although the past two decades have seen considerable progress, many questions remain. 
Young earth creationists also cite the following:
“In its simplest form, the Big Bang scenario doesn’t look like a good way to make galaxies. It allows too little time for the force of gravity by itself to gather ordinary matter—neutrons, protons and electrons—into the patterns of galaxies seen today. Yet the theory survives for want of a better idea.” Ivars Peterson, Science News, "Seeding the universe: how did matter assemble itself into the giant filaments, clusters, bubbles and walls of galaxies that now fill the universe?" March 24, 1990, p. 184.  
“It [the Great Wall, composed of tens of thousands of galaxies] is far too large and too massive to have formed by the mutual gravitational attraction of its member galaxies.” M. Mitchell Waldrop, “Astronomers Go Up Against the Great Wall,” Science, Vol. 246, 17 November 1989, p. 885. [See also Margaret J. Geller and John P. Huchra, “Mapping the Universe,” Science, Vol. 246, 17 November 1989, pp. 897–903. 
- Wile, Dr. Jay L. Exploring Creation With Physical Science. Apologia Educational Ministries, Inc. 1999, 2000