Spiral GalaxIes
- Spiral galaxies are the most common, out of all the galaxies that scientists have observed, 77% are spiral.
- The oldest observed spiral galaxy is about 10.7 billion years old.
- The largest spiral galaxy is 522,000 light-years across.
- Approximately two-thirds of all spiral galaxies are barred. Barred spiral galaxies are ones that have the shape structure of a bar in the middle.
- Many spiral galaxies contain a bulge in the center made up of dimmer, older stars and theoretically contains a black hole.
- A rotating disk orbits the bulge.
- This disk separates into arms that circle the entire galaxy.
- The arms contain bright, young stars that live a short life.
- Roughly 60% of spiral galaxies have multiple arms.
- Spiral galaxies are the most common, out of all the galaxies that scientists have observed, 77% are spiral.
Quiz
1. How old is the oldest known spiral galaxy?
2. What percentage of spiral galaxies are barred?
3. The stars in the arms of a galaxy life a/an _____ life.
4. What percentage of all of the galaxies that have ever been observed are spiral?
5. What percentage of spiral galaxies have multiple arms?