A '''spiral galaxy''' is a [[galaxy]] consisting of a rotating disk of [[star]]s, [[gas]] and [[dust]] which has a number of arms extending outwards from the galactic centre.<ref>[https://www.britannica.com/topic/galaxy/Types-of-galaxies#ref559197 Galaxies] from britannica.com</ref> Some spiral galaxies have a prominent bulge around the centre, while others have a bar crossing the centre with the spiral arms extending from the ends of the bar. They tend to be fairly large and blue in color. | A '''spiral galaxy''' is a [[galaxy]] consisting of a rotating disk of [[star]]s, [[gas]] and [[dust]] which has a number of arms extending outwards from the galactic centre.<ref>[https://www.britannica.com/topic/galaxy/Types-of-galaxies#ref559197 Galaxies] from britannica.com</ref> Some spiral galaxies have a prominent bulge around the centre, while others have a bar crossing the centre with the spiral arms extending from the ends of the bar. They tend to be fairly large and blue in color. |