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

Chapter 23: Our Galaxy and Chapter 24: Galaxies

Schematic Illustration of Our (Milky Way) Galaxy

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

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

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” ?

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.

Center of Our Milky Way Galaxy

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

Center of Milky Way Galaxy

More about Galaxies

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

(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

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

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

Distance Ladder

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

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

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

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

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