Galaxies are a group of stars that make up a system, which consists of more than one object called large and used by objects. Whereas, in astronomy, the notion of galaxies is a system of stars, dust and gas that is very wide, where the members have an attractive force (fact). A galaxy generally consists of stars that have very diverse colors, sizes and characteristics. Examples of galaxies, such as the Andromeda Galaxy and the Milky Way Galaxy where we spread the rules. Large galaxies are not found in a single form. The level of the galaxy is clumped in the cluster. For example the Milky Way galaxy is in a cluster called the Local Group.

Based on the morphology of galaxies are divided into three types, namely elliptical, spiral and irregular type galaxies. The division of this type of galaxy is based on the appearance or shape of these galaxies. The galaxies that are currently observed and studied by astronomers are composed of 5% irregular galaxies, 20% elliptical galaxies, and 75% spiral galaxies. The Milky Way galaxy is a type of spiral galaxy and a disk-like process, with a diameter of about 100,000 light years. Astronomers predict, the Milky Way galaxy consists of 100 billion stars. The center of the Milky Way galaxy is in the Sagittarius star cluster. It is estimated that the Milky Way galaxy lived 12-14 billion years.