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Milky Way - Our Planet
Milky Way is our home galaxy in the universe. It is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars. Earth is a part of the Milky Way Galaxy which, in turn, is a part of a cluster of galaxies known as the Local Group. Further, the Local Group is a small part of the Virgo Supercluster which is a cluster of cluster of galaxies, comprising of thousands of other galaxies. Like the Virgo Supercluster, there are countless other superclusters as well. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Then, observations by the American astronomer Edwin Hubble (November 20, 1889 - September 28, 1953) showed that the Milky Way is just one of many galaxies.