Answer the following question given this paragraph: 

Galaxies are divided into three types, according to shape. There are spiral galaxies, elliptical galaxies, and irregular galaxies. Spiral galaxies are a rotating disk of stars and dust. In the center is a dense bulge of material. Several arms spiral out from the center. Spiral galaxies have lots of gas and dust and many young stars. Figure below shows a spiral galaxy from the side. You can see the disk and central bulge.


Q: How many types of galaxies are there?


A:
three