22.3 Galaxies, Different Sizes and Shapes

CLICK ME!!!

Main Idea Detail Notes

1. The Milky Way is shaped like a disk with a bulge in the center.

1. Disk diameter is more than 100,000 light-years

1. The bulge is packed with stars about 26,000 light-years

1. Large faint layer of stars surrounds the disk and bulge

2. Because Earth is inside the disk, you have an edge-on view of the galaxy.

2. Appears as a band of blended star light2. Named after its hazy appearance2. Center is hidden by dust

Galaxies vary in appearance.

The objects in the Milky Way move in the following ways:

• Stars and nebulae orbit the center and very high speeds

• Sun is so large it takes 250 million years to orbit

Three Major Types of Galaxies

Spiral

Elliptical

Irregular

Old stars in

the disk

Young

er s

tars

in

the

arm

s

Arms

curv

e aw

ay

from

the

cent

er

Disk shaped

SpiralGalaxy

Arms of stars, gas and dust

Milky Way!

Elliptical Galaxy

• Made of mostly old stars

• Sphere or oval shaped

• Almost no dust or gas between stars

Maffei 1 is an elliptical galaxy in the constellation Cassiopeia. It is the closest giant elliptical galaxy to the Milky Way

NGC 1427A, an example of an irregular galaxy.

Irregular Galaxy

• Very faint or hard to see galaxies• They have no definite shape• Smallest type of galaxy• Fewest stars