Saturday, July 17, 2010

The local group of Galaxy



Galaxies tent to cluster together. The Milky Way galaxy belongs to a small cluster, consisting of at least 25 galaxies. Four are visible to the naked eye. One is a small spiral that can just be seen under good conditions in Triangulum. The others are the Andromeda galaxy and the large and Small Magellanic Clouds.
 The Local Group of galaxies is dominated by two spirals, the Milky Way galaxy and the Andromeda Galaxy, and the two are often compared. Both are larger than the average spiral, but Andromeda is twice as broad as ours and the largest member of the Local Group. It is approaching our galaxy at a speed of 275 Km/Sec – negligible speed in comparison with its distance of over two million light years.
The Local group contains hundred trillion members. They contain little gas, and a few young stars, so they are predominantly reddish in color. There are no large elliptical galaxies in the Local Group, but some small ones are satellite galaxies of Andromeda.  The large and Small Magellanic clouds are satellite galaxies of the Milky Way. They are visible as two patches of light close to the Milky Way in the Southern Sky. The Large Magellanic Cloud is 170,000 light years distance and 30,000 light years. The Small Magellanic Cloud is 190,000 light years away and 16,000 light years diameter. Both are classified as spiral, though they have been heavily distorted by the Milky Way.