Galactic type EssayGalaxies can be explained as massive systems of stars, dust, gas as well as other types of matter that are bound together by gravitational forces to form a single physical mass. As Binney and Merrifield (1998: p 34) explain, on the basis of extensive imaging surveys that have been carried out, it is estimated that there are more than 40 billion galaxies in the universe, that are spread out in a complex large-scale systems for example, clusters, super-clusters. There are also boundaries of huge empty spaces referred to as voids. The sun is just part of galaxy called the Milky Way. This galaxy is a much flattened spiral galaxy that could be comprised by more than 400 billions stars. Through the use of telescopes, it is possible to view these galaxies. Gravitational Lenses Gravitational lenses can be described as galaxies and clusters of galaxies, which are so huge that they cause bends to the route of light objects towards their directions, thus they distort the forms of backdrop galaxies into curves as well as rings.