The Galaxy is composed of stars, gas and dust that are held together by the force of the gravity. There are thousands of galaxies in the universe that are observed and taken with photographs with astronomers. Some of them are found to be alone in space while the other galaxies are clustered in groups. Clustered galaxies may contain few galaxies or several galaxies; some reach up to thousands.
Galaxies differ in their sizes; some of them are giants and the others are dwarf. The diameter of the largest galaxy is about 192,000 light-years while the diameter of the smallest known galaxy
is about 6600 light-years.The solar system consists of our sun and the nine planets including the Earth belong to the Milky Way galaxy. This galaxy has an estimated 200 billion stars including the sun. The brightest part of the Milky Way galaxy lies in the constellation of Sagittarius. In the Southern Hemisphere, it passes through the Cassiopeia constellations and Cygnus constellations while in the Northern Hemisphere; it passes through the Southern Cross constellation and Scorpio constellation.
The scientist and astronomers had classified the galaxies in the universe in accordance to their appearance and shape. Galaxies are different in their shape and appearance; some galaxies are Spiral, the others are elliptical and the others are irregulars.
Our galaxy, the Milky Way is within the cluster of galaxies named as the Local Group. There are different shapes of galaxies in this group; some galaxies are irregular, others are spiral while the others are elliptical.
In Spiral galaxies, there are bulges or nucleus and
in here, several arms may come out consisting of dust and stars. Few stars also exist between these arms. Some Spiral galaxies are classified in accordance to how open their arms; these classifications are S2, Sb and Sc. Sba, SBb and SBc are used to classify the galaxies with arms that extend from a bar of stars in the nucleus; they are called as “barred” spirals; some other galaxies are designated as S0; they are Spiral galaxies which have no arms.The Elliptical galaxy is considered as the most common type of galaxy. From elliptical shape, they range from almost spherical to a flattened disk-like shape. The Elliptical galaxies that are almost spherical are designated as E0 galaxies. The Elliptical galaxies that are less spherical are designated as E3 galaxies. The Elliptical galaxies that are flattened are designated as E7 galaxies. Some Elliptical galaxies are found to be small while other Elliptical galaxies are very large.
The Magellanic Clouds are the nearest neighbors of the Milky Way in the Space. The Large and the Small Magellanic Clouds are just two of the four Irregular galaxies that can be found in the Local Group from where the Milky Way galaxy also belongs.
The Large Magellanic Cloud is about 38400 light-years in diameter and it is visible with the naked eye when seen from the Southern Hemisphere. The Small Magellanic Cloud is only about 19 light years in its diameter.