Artwork showing five common types of galaxy. Clockwise from top left these are: spiral, lenticular, barred spiral, elliptical and irregular. Elliptical galaxies are common, and contain mainly old stars. They also have relatively less gas and dust than the other types. Lenticular galaxies are disc-shaped, but lack a well- differentiated nucleus or spiral arms. Spiral galaxies, like our own Milky Way, tend to have a nucleus of older stars, and hot gas, dust and young stars making up the spiral arms. Irregular galaxies tend to be small, and are commonly found as companions of larger galaxies, as the Magellanic Clouds are to the Milky Way.