Shapes

• There are three shapes of galaxies: spiral, elliptical and irregular. Spiral galaxies are shaped like disks, bulging in the center with arms revolving around. Elliptical galaxies are round or flattened globes that rotate very slowly. Irregular galaxies are puffy and odd shaped, containing dust and many blue stars.
  
  

Origin

• There are two theories about the origins of galaxies: the top-down theory and the bottom-up theory. The top-down theory suggests galaxies formed out of larger
  "super-galaxies" and broke apart. The bottom-up theory suggests galaxies started as globular clusters and merged together.
  
  

Shift in Spectra

• A red shift in the electromagnetic spectra of a galaxy indicates it is moving away from Earth. A blue shift in the electromagnetic spectra of a galaxy indicates it is moving toward Earth.
  
  

Milky Way Galaxy

• Our solar system is in one of the arms of the Milky Way Galaxy about 25,000 light years from the center of the galaxy. The Milky Way is about 100,000 light years across and contains about 100 billion stars.
  
  

Closest Galaxies

• There are only three galaxies that are visible to the naked eye from Earth. Andromeda galaxy is 2 million light years away. The Large Magellanic Cloud is 160,000 light years away. And the Small Magellanic Cloud is 180,000 light years away.