Galaxies are the groups of billions of stars that are held together by the force of gravity. The galaxies either the shape of spiral or elliptical, while the others are irregular in shape.
The Milky Way:
The best galaxy is the Milky Way. The word galaxy is derived form the Greek word for milk. This is because, when we view the galaxy through a telescope, they prove that they are made of individual stars, they looked like milky or cloudy areas in the sky. Our relatively small Solar system is only one of 100-200 billion stars in the Milky Way galaxy, which is 100,000 light years in diameter. The Sun and all the planets nearly takes about 200,000,000 years to complete one rotation around its center.
The largest galaxy is the Central galaxy of the Abell 2029 galaxy cluster, discovered in 1990. It is 1,070 million light years distant and it has a diameter of about 5.6 million light years. It is nearly 80 times the diameter of our own galaxy. It has a total light output equivalent to two trillion times that of the sun.
The brightest of all the galaxies is the Large Magellanic Cloud, which is seen only in the southern hemisphere. It is 170,000 lights years from the Earth and 39,000 light years in diameter.
The Sagttarius Dwarf, which was discovered in 1994, is more than 70,000 light years from Earth, and is being torn apart.
Most Distant Galaxy:
In 2004, astronomers at the European Southern Observatory, Chile, announced the discovery of Galaxy Abell 135 IR 1916. Its is nearly 13.2 billion light years from Earth.
Farthest visible Galaxy:
The most distant galaxy that could be viewed with a naked eye is the Andromeda Galaxy, which is 2,309,000 light years form the Earth. This galaxy has 300 billion stars and a diameter of 180,000 light years.