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MILKY WAY |
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MILKY WAY Our home in the Universe is the Milky Way Galaxy. If you could look down on the Milky Way from above, the view would be rather like flying over a glittering city at night. The Sun is just one of the 200 billion stars that inhabit this space city. Mingled in with the stars are vast clouds of dust and gas, the material from which future stars will be made. In places, the clouds are pierced by brilliant nebulas in which stars have just formed. The Milky Way is a spinning, spiral-shaped galaxy 100,00 light years (ly) across, but only 2,000 ly thick. It started life billions of years ago as a vast, round cloud of gas that collapsed under the force of its own gravity, and was then flattened by its rotation into its present shape. STRUCTURE OF THE MILKY WAY Mapping the objects in our Galaxy reveals
its true shape. Two major spiral arms, and segments of the other, wind around an elongated
central bulge. Bright young stars, pinkly glowing nebulas of gas and dust, and dense, dark
molecular clouds trace out the shape of the arms. By contrast, the central bulge contains
little gas and mainly consists of old stars. |
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