Kierrepyörregalakseiksi

Kierrepyörregalakseiksi, often referred to as spiral galaxies, are a common type of galaxy characterized by their distinctive spiral arms. These arms are regions of active star formation, appearing brighter and bluer than the central bulge of the galaxy due to the presence of young, hot stars. The spiral structure is thought to be caused by density waves propagating through the galactic disk.

Our own Milky Way galaxy is a spiral galaxy. These galaxies typically contain a central bulge, a flattened disk, and a surrounding halo. The bulge is a roughly spherical collection of older stars, while the disk contains stars, gas, and dust arranged in a flattened plane. The halo is a much larger, diffuse region that contains globular clusters and a significant amount of dark matter.

Spiral galaxies come in various forms, classified by their degree of spiral structure and the size of their central bulge. Some have tightly wound arms and prominent bulges, while others have loose, open arms and small bulges. Barred spiral galaxies are a subtype where a bar-shaped structure of stars extends across the central bulge, with the spiral arms originating from the ends of the bar. The formation and evolution of spiral galaxies are complex and are influenced by factors such as galactic mergers and interactions with other galaxies.