1. ASTR 1102-002 2008 Fall Semester [Slides from Lecture20]
Joel E. Tohline, Alumni Professor
Office: 247 Nicholson Hall
[Slides from Lecture20]

2. Chapter 23: Our Galaxy and Chapter 24: Galaxies

3. Schematic Illustrationof
Our (Milky Way) Galaxy

6. Stellar Populations Pop I Pop II Location Galaxy’s disk
Throughout Galaxy’s “halo”
Kinematics
Circular orbits in the disk
Significant motion out of the disk
Metallicity
High
Low

8. Stellar Populations Pop I Pop II Location Galaxy’s disk
Throughout Galaxy’s “halo”
Kinematics
Circular orbits in the disk
Significant motion out of the disk
Metallicity
High
Low
Age
Young
Old

9. Stellar Populations What about “Pop III” ? Pop I Pop II Location
Galaxy’s disk
Throughout Galaxy’s “halo”
Kinematics
Circular orbits in the disk
Significant motion out of the disk
Metallicity
High
Low
Age
Young
Old
What about “Pop III” ?

10. Stellar Populations
We are only able to study and delineate well these different stellar populations in our own MW Galaxy
The presumption is that all other galaxies contain these same populations of stars, although the fraction of stars belonging to Pop I vs. Pop II varies from galaxy to galaxy.

11. Center of Our Milky Way Galaxy

12. Center of Our Milky Way Galaxy
Evidence for a Massive Black Hole
at the
Center of Our Milky Way Galaxy

13. Center of Milky Way Galaxy

14. More about Galaxies

15. Individual Stars…(early in the semester)
Location in Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion)
Motion toward/away from us (radial velocity)
Intrinsic properties
Brightness (luminosity/magnitude)
Color (surface temperature)
Mass
Age

16. (now let’s discuss)…Individual Galaxies
Location in Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion)
Motion toward/away from us (radial velocity)
Intrinsic properties
Brightness (luminosity/magnitude)
Color (surface temperature)
Mass
Age

17. Individual Galaxies Location in Space
Coordinate (angular) position on the sky

21. Individual Galaxies Location in Space
Coordinate (angular) position on the sky
Distance from Earth

22. Distance Ladder

25. Individual Galaxies Location in Space Motion through Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion) – None observable!
Motion toward/away from us (radial velocity) – Extremely revealing discovery made by Slipher, Hubble, Humason

26. Individual Galaxies Location in Space Motion through Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion) – None observable!
Motion toward/away from us (radial velocity) – Extremely revealing discovery made by Slipher, Hubble, Humason

27. Individual Galaxies Location in Space Motion through Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion) – None observable!
Motion toward/away from us (radial velocity) – Extremely revealing discovery made by Slipher, Hubble, Humason

28. Individual Galaxies Location in Space Motion through Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion) – None observable!
Motion toward/away from us (radial velocity) – Extremely revealing discovery made by Slipher, Hubble, Humason

29. Individual Galaxies Location in Space Motion through Space
Coordinate (angular) position on the sky
Distance from Earth
Motion through Space
Motion across the sky (“proper” motion) – None observable!
Motion toward/away from us (radial velocity) – Extremely revealing discovery made by Slipher, Hubble, Humason