Slide 16 of 49

As stated previously, life requires that the planetary system be housed in a spiral galaxy, such as that seen above. Not only must the planetary system be located in a spiral galaxy, but it must be located away from the center of that galaxy. Take a close look at the center of the galaxy above. There are some powerful forces acting in the center of this galaxy that are spewing gases (the red "flames") well above the galactic disk. A planetary system located near the center of the galaxy would receive too much radiation for lifeforms to exist. In addition, stellar gravitational interactions would most likely disrupt planetary orbits in such crowded conditions before the planet was suitably prepared for life to exist.