The diameters of these clusters range from about 75 light years to as much as 400 light years and can be as far as 300,000 light years from the Earth. In many parts of the Milky Way galaxy, there exist dense concentrations of interstellar matter known as nebula and are generally classified as emission nebula, reflection nebula or dark nebula. Emission nebula are by far the most exotic, for they contain one or more extremely hot and luminous type O or B. stars (i.e. gas giants). The ultraviolet light form the stars within this type of nebula "excites hydrogen and oxygen atoms which gives these nebulae their characteristic greenish-yellow and red glows." An excellent example is the Great Nebula in the constellation...

According to the currently-accepted theory of the Big Bang, most astronomers estimate that the age of the Milky Way galaxy is proportionate to the age of the universe itself which lies somewhere between 10 billion and 20 billion years with 15 billion years as the accepted average. If this estimate is true, then the Milky
Way galaxy is indeed extremely ancient and will continue to move within the universe for billions of years to…