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The Hercules Cluster is situated approximately 500 million light-years away. It is an archipelago of island universes. The Hercules Cluster can also be referred to as Abell 2151. It is high in gas and dust, which are the ingredients for forming stars. This produces spiral galaxies. On the other hand, elliptical galaxies are sparse because there is not enough gas and dust to create them. In this image, the blue color represents the new forming galaxies, and the yellow color depicts the aging galaxies. The cluster center's size represents the actual size of about 6 million light-years. Cluster galaxies interact and therefore some seem to be impacting one another. An example for this would be the Hercules Cluster, which is effected by smaller galaxy clusters.

Galaxies in the Hercules Cluster contain metal elements. These are seen from emission spectroscopy lines. The Hercules cluster is composed of three hundred thousand stars held in a spherical shape due to gravity and is 25,000 light years from Earth. It’s also known as the great globular cluster, and is known as the brightest, and therefore can be seen by the human eye within the constellation Hercules. The cluster’s location within the Hercules’s constellation gives it its name. The name Hercules dates back to the Greek myth of Heracles.

It was recorded in 1714 by Edmond Halley as a starless nebula. Fifty years later, the cluster received its scientific title as M13 by Charles Messier. In 1787, William Herschel, using his developed telescope, saw that the cluster was made of stars. Later scientists refereed to the shape as spilled salt. As technology progressed, the telescopes allowed the scientists to study the cluster in more detail. Scientists found that stars in the Hercules cluster are extreme population II stars that are poor in heavy elements. The age of the stars is noted to be about 12 billion years old. (Shubinski, n.d., pp. 64-67).