AST 301 — Unit Eight Outline

Prof. Paul R. Shapiro
Unit Eight: The Milky Way Galaxy

(1) General Overview of M-W Galaxy
      (a) size, shape, structure
            (i) flattened disk
            (ii) spheroidal bulge
            (iii) halo
            (iv) nucleus
            (v) globular clusters
            (vi) spiral arms
            (vii)solar location

(2) History
      (a) Galileo and telscope resolves M-W into stars
      (b) William Herschel and "star counts": M-W is a disk (but looks like we are at the center)
      (c) Harlow Shapley and globular clusters: RR Lyrae variable stars indicate distance to globular clusters
            (i) locates Galactic Center ("GC")
            (ii) we are NOT at center of M-W

(3) Galactic Rotation
      (a) Jan Oort and stellar Doppler shifts: pattern of radial velocities shows that stars orbit the GC
      (b) Rotation Curve and Kepler's Third Law: The Mass of the Galaxy
            (i) explaining the rigid rotation of inner galaxy
            (ii) measure mass interior to Sun's orbit around GC
            (iii) Detect "dark matter": Flat rotation curve of outer galaxy shows that mass distribution continues out past the last starlight

(4) Spiral Arms
      (a) Density Waves

(5) The Nucleus

(6) The Halo

(7) The Globular Clusters
      (a) contrast of Globular vs. Open Clusters

(8) Two Stellar Populations: Pop I vs. Pop II

(9) The Interstellar Medium		 link to outline
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The University of Texas at Austin Department of Astronomy Astrophysics Theory Group