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, with arms extending out of a nucleus
  • Spiral galaxy, with smooth arms extending out of a nucleus
  • Elliptical galaxy, shaped like spheres or ellipsoids
  • Irregular galaxy, with 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?