A Galaxy is a group of stars and planetary systems. We live in the Milky Way Galaxy, a spiral Galaxy.


Many types of galaxies exist:

  • Barred Spiral, which have arms extending out of a nucleus
  • Spiral, with smooth arms extending out of a nucleus
  • Elliptical, which are shaped like spheres or ellipsoids
  • Irregular, which have no definite shape

There must be at least 100 million galaxies in the universe.


Galileo looked up at the milky streak that divides the night sky and proposed that it might be the aggregate light from millions of stars, very far away.

Edwin Hubble?