A galaxy is a huge collection of stars, dust, and gas. Galaxies are found in single or large groups called superclusters. It is believed that more than 100 billion galaxies are scattered through the universe.

All galaxies do not look alike. They vary greatly in shape and size. Based on their shape and appearance, galaxies can be divided into three broad categories: spiral, elliptical, and irregular. Galaxies can range from a few thousand to half a million light-years in size. All the stars that we see in the night sky belong to the milky way galaxy.






Cluster: 
Galaxies are found in groups known as clusters. These clusters are bound together by mutual gravitational attraction, intergalactic gas, and dark matter. The cluster generally consists of 50-1000 galaxies. Various clusters and groups of galaxies together form superclusters. Our galaxy, the Milky Way, belongs to the cluster Local Group. The Virgo Cluster, Hercules Cluster, and the Coma Cluster are a few other examples of galaxy clusters.







Elliptical Galaxies:
Elliptical galaxies are shaped like an ellipse. They have a bright nucleus and are mostly made up of older stars, with very little gas and dust. About 10per cent of the observed galaxies are elliptical galaxies. Elliptical galaxies vary greatly in size. They range from very smallones found near our own galaxy to the gaint elliptical galaxy. It is one of the largest galaxies of the universe.







Spiral Galaxies: 
Spiral galaxies are galaxies that resemble a disk. They have a central nucleus with spiral arms extending outwards. The arms have many hot, young, blue and blue-white stars and are regions of active star formation. The stars make the arms easily visible. Most spiral galaxies are made up of middle-aged stars. The M100 Galaxy in the Virgo Cluster is an example of a sipral galaxy.







Irregular Galaxies: 
Irregular galaxies are neither elliptical nor spiral. They have little symmetry in their structure. Irregular galaxies are formed when two galaxies collide or come close to one another and their gravitational forces interact. Scientist believe that these galaxies have an irregular shape as they are young and are yet to reach a symmetrical state. The M82 is an example of an irregular galaxy.







Triangulum Galaxy:
The Triangulum Galaxy is a neighboring galaxy of the Milky Way. It is s Spiral galaxy located in the constellation Triangulum. The Triangulum Galaxy is smaller than the Milky Way Galaxy and the Andromeda Galaxy. It was discovered by Giovanni Batista Hodierna around 1654.







Andromeda Galaxy: 
The Andromeda is a spiral galaxy near the Milky Way Galaxy. It is known as Messier 31, M31, or NGC 224. It was first discovered by the Persian astronomer Abd Al-Rahman Al Sufi in AD 905. The galaxy is easily visible to the naked eye in a moderately dark sky. it is generally considered to be the penultimate distant object visible to the naked eye after Triangulum.