A Brief Overview of the Motions of Galaxies Within Our Universe

Our universe can be seen as a chain, and every part of the universe is a link in the chain. Every planet is a part of a solar system, every solar system a part of a galaxy, every galaxy a part of a cluster, every cluster a part of a super cluster, and every super cluster is a part of our universe. There are an infinite number of links, but one of the most fascinating parts of our universe is galaxies and their motions. Each galaxy has specific motions within itself and in correlation to other galaxies. Even galaxy clusters interact with other galaxy clusters within our universe. Galaxies are what set the entire universe into motion.

A galaxy is a huge collection of a few hundred million to over a trillion stars and other galactic matter bound by gravity. In the early 1800’s through the 1900’s, galaxies were undefined. They were seen as fuzzy patches of light in the sky, classified as nebulae. In 1917 Harlow Shapley suggested that the nebulae were actually distant star systems that were outside of our own star system (Marvel 153-154). Further research and advanced technology confirmed Shapley’s discovery and these galaxies are classified into three different types: Spiral, elliptical, and irregular. Our solar system is located in the Milky Way Galaxy, which is a spiral galaxy. Each type of galaxy has a special type of motion within itself.

Spiral galaxies make up about 77% of all the galaxies in the universe. They are large disks of stars. Inside the disk of stars is a smaller disk of gas and dust where many of the new stars are formed (Marvel 156). In the inner regions of the disk, objects move in solid-body rotation. This type of rotation means that the angular velocity is constant with the distance from the center of rotation. This kind of rotation can be seen if you were to twirl a baton. The outer parts of the baton rotate at the same angular speed as the inner. In reality, the outer portion has to move faster than the inner to keep the same angular velocity. After a certain distance, differential rotation begins within a spiral galaxy.