Chapter 14 Our Galaxy 14 1 The Milky

Chapter 14 Our Galaxy

14. 1 The Milky Way Revealed • Our Goals for Learning • What does our galaxy look like? • How do stars orbit in our galaxy?

What does our galaxy look like?

The Milky Way galaxy appears in our sky as a faint band of light

Dusty gas clouds obscure our view because they absorb visible light This is the interstellar medium that makes new star systems

If we could see the Milky Way from above the disk, we’d see its spiral arms and other components, including a central bar…

The Milky Way Galaxy also has a bar of stars and gas in its center

How do stars orbit in our galaxy?

Stars in the disk all orbit in the same direction with a little motion above then below the disk (due to gravity of disk)

Orbits of stars in the bulge and halo have random orientations

Sun’s orbital motion (radius and velocity) tells us mass within Sun’s orbit: 1. 0 x 1011 MSun

What have we learned? • What does our galaxy look like? • The Milky Way Galaxy consists of a thin disk about 100, 000 light-years in diameter with a central bulge and a spherical region called the halo that surrounds the entire disk. The disk contains the gas and dust of the interstellar medium, while the halo contains very little gas.

What have we learned? • How do stars orbit in our galaxy? • Stars in the disk all orbit the galactic center in about the same plane and in the same direction. Halo and bulge stars also orbit the center of the galaxy, but their orbits are randomly inclined to the disk of the galaxy.

Activity #14, page 45 -47