Galaxies

1. Galaxies 19.3

2. Elliptical Galaxies • Galaxies that have flat roundish shapes like a football • Contain billions of stars but have little gas and dust. • Contain mature or old stars – not new ones

3. Irregular Galaxies • Do not have regular shapes • Typically smaller than other galaxy shapes • Have many bright young stars • Have lots of gas and dust to form new stars

4. Spiral Galaxies • Appear to have a bulge of stars in the center and arms that spiral outward • There are some that have a bar through the bulge with arms spiraling outward from the bar – barred-spiral galaxy • Bulge contains densely packed older stars but little gas and dust. • Outer arms contain younger stars and nebulae for more stars to form

5. Milky Way • Our solar system is in a spiral galaxy called the Milky Way, two thirds of the way out one arm • Recent evidence suggests that the Milky Way may be a barred- spiral galaxy • From the side it looks like a narrow disk with a bulge in the middle • From the top or bottom viewpoint the spiral shape is visible. • The center of our galaxy is about 25,000 light years away from us.