Spiral Galaxies
- Structure: Have a central bulge surrounded by a flat, rotating disk with spiral arms extending outward. The disk contains stars, gas, and dust, while the bulge is mainly made of older stars.
- Appearance: Often exhibit well-defined spiral arms that can be seen in various stages of winding.
- Normal Spiral Galaxies: Have prominent spiral arms. Example: The Milky Way, our home galaxy.
- Barred Spiral Galaxies: Feature a central bar-shaped structure composed of stars with spiral arms extending from the ends of the bar. Example: Messier 81 (M81).
- Lenticular Galaxies: Intermediate between spiral and elliptical galaxies, they have a disk-like structure but lack significant spiral arms. Example: NGC 5866.
