Galaxies come in different shapes, sizes, and classifications. The main shapes are spiral, elliptical, and irregular. Spiral galaxies are disk-shaped with spiral arms radiating from the center. Elliptical galaxies have older stars distributed in an oval shape. Irregular galaxies have an uncommon shape and contain young stars, gas, and dust. Our own galaxy, the Milky Way, is a large spiral galaxy containing about 200 billion stars.