Andrew Gaspar, LA. asked:
I understand that there are two types of galaxies. Some have spiral arms and others an elliptical shape. What processes would form those two different types?
We think with galaxy formation that everything was very hot after the big bang, so you start off with this enormous cloud of very hot gas that begins to cool. As the gas cools, it starts off radiating x-rays, it cools down more and eventually it condenses down into the stars that form a galaxy.
If you have a large cloud of gas which is quite static, it will condense into an elliptical shaped galaxy.
If itís rotating even very slightly, the galaxies that condense from it will end up disc-shaped such as the spiral shape our Milky Way is.