Spiral Galaxies

Spiral galaxies are a common type of galaxy in the universe. They are characterized by their spiral arms that extend outward from the center of the galaxy. These arms are made up of stars, gas, and dust, and they give the galaxy its spiral shape.

Structure of Spiral Galaxies

Spiral galaxies have a central bulge, which contains older stars, and a flat disk where younger stars are found. The spiral arms are located in the disk and are where new stars are formed. The arms are believed to be created by density waves that move through the galactic disk, compressing the gas and dust to form new stars.

Types of Spiral Galaxies

There are two main types of spiral galaxies: normal (or unbarred) and barred spiral galaxies. Normal spiral galaxies have a central bulge with spiral arms extending from it, while barred spiral galaxies have a bar-like structure running through the central bulge, with the spiral arms extending from the ends of the bar.

Study Guide

1. What are the main characteristics of spiral galaxies?
2. Describe the structure of a spiral galaxy.
3. What are the two main types of spiral galaxies?
4. How are spiral arms formed in a spiral galaxy?

Understanding the structure and classification of spiral galaxies is key to exploring the diversity of galaxies in the universe. Keep exploring and learning about the wonders of outer space!