Spiral galaxies.
These galaxies are conspicuous for their spiral-shaped arms, which emanate from or near the nucleus and gradually wind outward to the edge. There are usually two opposing arms arranged symmetrically around the centre. The nucleus of a spiral galaxy is a sharp-peaked area of smooth texture, which can be quite small or, in some cases, can make up the bulk of the galaxy. The arms are embedded in a thin disk of stars. Both the arms and the disk of a spiral system are blue in colour, whereas its central areas are red like an elliptical galaxy.