Constellations are shapes in the sky, like join-the- dots figures. There are no real "patterns" in the sky, rather we see a more or less random array of bright and dim stars. Each culture has found its own gods, heroes and villains enshrined in the sky. In addition to providing cheap, omnipresent monuments for cultural icons, the human constructed "patterns" help cultures encode valuable information about the year: for example, the proper time to plant and reap crops. Constellations are visual mnemonics to help remember the near random pattern of the sky. The Web dictionary defines a star cluster as: Aggregations of stars that are gravitationally bound, but are smaller and less massive than galaxies. Star clusters are groups of stars whose members are sufficiently close to each other to be physically associated. The clusters which are spherically symmetric and compact containing from several ten thousands to may be a million stars that are thought to share a common origin are called globular clusters. The open (galactic) clusters are much less dense and contain at most few thousand stars, sometimes less than 20. One theory of how star clusters are formed is this: When Galaxies pass close to each other some times a small cluster of stars will be pulled away from the galaxy towards the stronger gravitational pull, these clusters then travel around the universe. Another is this: Stars in a cluster are similar to one another in age and composition and are believed to have formed from the same interstellar cloud at about the same time. The stars in a cluster are gravitationally bound to one another and travel through space together. Its like a smaller galaxy. The actual difference between constellations and star clusters is that a cluster is a group of stars physically related to each other, whereas a constellation is a random pattern of stars viewed from Earth.