Year milestone 1962

Irregular Galaxies

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  The irregular galaxies comprise about one-tenth of all galaxies.
  
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  The stars of the irregular galaxies are generally very old.
  

Our Galaxy (the Milky Way)

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  The Milky Way is the galaxy that hosts our solar system. It is shaped like a flat disc with a central bulge.
  
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  Its diameter is between 1,50,000 and 2,00,000 light-years.
  
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  In the nucleus, the thickness reaches 10,000 light-years, whereas in the disc it is 500-2,000 light-years thick.
  
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  It is estimated to contain 100-400 billion stars.
  
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  The inner stars travel faster than those further out.
  
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  The Solar System is located in the Orion Arm, 26,000 light-years from the center (about one-third from the center) of the Milky Way galaxy.
  
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  The Sun completes one lap of the galaxy in about every 220 million years.
  
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  The solar system revolves around the Milky Way with a speed of 285 km per second.
  
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  The Andromeda Galaxy is the closest galaxy (spiral) to us – being 2 million light-years away.