Elliptical galaxies contain almost no gas and dust which indicates that there are no newly forming stars. Most of the stars are older or red giants, thus giving the galaxy a reddish tint. The S0 galaxy is the intermediate between elliptical and other spiral galaxies. It exhibits very little gas, dust, and very few hot, bright stars. There are no obvious spiral arms, but appears only as a disk with a large nucleus.
Spiral galaxies make up over two-thirds of all known galaxies.
Sc spirals are known for their large clouds of gas and dust, small nuclear bulge and very loosely wound arms. The Sb galaxy is somewhere in between the two. There is more gas and dust in Sb and Sc galaxies which means there are more young, hot, bright stars giving the galaxies a blue tint. The Andromeda and Milky Way galaxies are examples of Sb spirals. They are very similar to the regular spirals but they have a more elongated nuclear bulge.